GN: New conventions, default target and refactorings

GN: New conventions, default target and refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree,
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled.

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#Can-I-control-what-targets-are-built-by-default).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to 6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
NOTRY=True

Committed: https://crrev.com/6ceab083225dfa485bb48f9e43231c216acccbaf
Cr-Commit-Position: refs/heads/master@{#14821}

[kjellander_webrtc, 2016-10-24 11:15:30]

Description was changed from

==========
GN: Add default target + refactorings

This CL assumes each GN target is one of 4 categories:
* Production code
* Tests
* Examples
* Tools
The first two have targets all over the tree, while the latter is isolated to
the examples/ and tools/ directories.

Change the //webrtc:webrtc_tests target to become a group that compiles
all WebRTC tests. Add a few new group targets in directories that contain
multiple tests, to avoid having to list all in //webrtc:webrtc_tests.

Rename 'root' target at the root level to 'default' and make it depend on
everything we want to build. Having this, what's built is explicit instead of
building all generated GN targets (which adds a lot of unnecessary
objects to be compiled). This cuts down the number of compiled objects
on Android from 8855 to 6276.

Refactorings:
* move webrtc/video/ targets from webrtc/BUILD.gn into webrtc/video/BUILD.gn
* add new target 'run_tests' in webrtc/test/BUILD.gn

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

to

==========
GN: Add default target + refactorings

This CL assumes each GN target is one of 4 categories:
* Production code
* Tests
* Examples
* Tools
The first two have targets all over the tree, while the latter is isolated to
the examples/ and tools/ directories.

Change the //webrtc:webrtc_tests target to become a group that compiles
all WebRTC tests. Add a few new group targets in directories that contain
multiple tests, to avoid having to list all in //webrtc:webrtc_tests.

Rename 'root' target at the root level to 'default' and make it depend on
everything we want to build. Having this, what's built is explicit instead of
building all generated GN targets (which adds a lot of unnecessary
objects to be compiled). This cuts down the number of compiled objects
on Android from 8855 to 6276.

Refactorings:
* move webrtc/video/ targets from webrtc/BUILD.gn into webrtc/video/BUILD.gn
* add new target 'run_tests' in webrtc/test/BUILD.gn

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

[kjellander_webrtc, 2016-10-24 11:15:30]

kjellander@webrtc.org changed reviewers:
+ ehmaldonado@webrtc.org

[kjellander_webrtc, 2016-10-24 11:15:51]

Will run WebRTC tryjobs in PS#2.

[kjellander_webrtc, 2016-10-24 11:55:22]

Patchset #1 (id:1) has been deleted

[kjellander_webrtc, 2016-10-24 11:56:55]

Description was changed from

==========
GN: Add default target + refactorings

This CL assumes each GN target is one of 4 categories:
* Production code
* Tests
* Examples
* Tools
The first two have targets all over the tree, while the latter is isolated to
the examples/ and tools/ directories.

Change the //webrtc:webrtc_tests target to become a group that compiles
all WebRTC tests. Add a few new group targets in directories that contain
multiple tests, to avoid having to list all in //webrtc:webrtc_tests.

Rename 'root' target at the root level to 'default' and make it depend on
everything we want to build. Having this, what's built is explicit instead of
building all generated GN targets (which adds a lot of unnecessary
objects to be compiled). This cuts down the number of compiled objects
on Android from 8855 to 6276.

Refactorings:
* move webrtc/video/ targets from webrtc/BUILD.gn into webrtc/video/BUILD.gn
* add new target 'run_tests' in webrtc/test/BUILD.gn

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

to

==========
GN: Add default target + refactorings

This CL assumes each GN target is one of 4 categories:
* Production code
* Tests
* Examples
* Tools
The first two have targets all over the tree, while the latter is isolated to
the examples/ and tools/ directories.

Change the //webrtc:webrtc_tests target to become a group that compiles
all WebRTC tests. Add a few new group targets in directories that contain
multiple tests, to avoid having to list all in //webrtc:webrtc_tests.

Rename 'root' target at the root level to 'default' and make it depend on
everything we want to build. Having this, what's built is explicit instead of
building all generated GN targets (which adds a lot of unnecessary
objects to be compiled). This cuts down the number of compiled objects
on Android from 8855 to 6276.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

[kjellander_webrtc, 2016-10-24 12:04:50]

Description was changed from

==========
GN: Add default target + refactorings

This CL assumes each GN target is one of 4 categories:
* Production code
* Tests
* Examples
* Tools
The first two have targets all over the tree, while the latter is isolated to
the examples/ and tools/ directories.

Change the //webrtc:webrtc_tests target to become a group that compiles
all WebRTC tests. Add a few new group targets in directories that contain
multiple tests, to avoid having to list all in //webrtc:webrtc_tests.

Rename 'root' target at the root level to 'default' and make it depend on
everything we want to build. Having this, what's built is explicit instead of
building all generated GN targets (which adds a lot of unnecessary
objects to be compiled). This cuts down the number of compiled objects
on Android from 8855 to 6276.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

to

==========
GN: Add default target + refactorings

This CL assumes each GN target is one of 4 categories:
* Production code
* Tests
* Examples
* Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

A new convention is also introduced: Each directory's BUILD.gn file
shall contain a target named similar to the directroy name. This target
is supposed to contain the 'most common' production code, i.e. 
so that most consumers of the directory can depend on only the directory
(without specifying which target inside it they need).

//webrtc:webrtc_tests is changed to become a group that compiles
all WebRTC tests. A few more new group targets are created in directories
that contain multiple tests, to avoid having to list all in
//webrtc:webrtc_tests.

The 'root' target at the top level is renamed to 'default' and now depend on
everything we want to build. Having this, what's built is explicit instead of
building all generated GN targets (which adds a lot of unnecessary
objects to be compiled). This cuts down the number of compiled objects
on Android from 8855 to 6276.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

[kjellander_webrtc, 2016-10-24 12:53:53]

On 2016/10/24 11:15:51, kjellander_webrtc wrote:
> Will run WebRTC tryjobs in PS#2.

The baremetal failure was caused by a stale test that is now removed.

[ehmaldonado_chromium, 2016-10-24 13:00:20]

On 2016/10/24 12:53:53, kjellander_webrtc wrote:
> On 2016/10/24 11:15:51, kjellander_webrtc wrote:
> > Will run WebRTC tryjobs in PS#2.
> 
> The baremetal failure was caused by a stale test that is now removed.

Can you fire the swarming bots too, please?

[kjellander_webrtc, 2016-10-26 11:09:15]

On 2016/10/24 13:00:20, ehmaldonado_chromium wrote:
> On 2016/10/24 12:53:53, kjellander_webrtc wrote:
> > On 2016/10/24 11:15:51, kjellander_webrtc wrote:
> > > Will run WebRTC tryjobs in PS#2.
> > 
> > The baremetal failure was caused by a stale test that is now removed.
> 
> Can you fire the swarming bots too, please?

Done, and they're green.

[ehmaldonado_webrtc, 2016-10-26 11:09:46]

On 2016/10/26 11:09:15, kjellander_webrtc wrote:
> On 2016/10/24 13:00:20, ehmaldonado_chromium wrote:
> > On 2016/10/24 12:53:53, kjellander_webrtc wrote:
> > > On 2016/10/24 11:15:51, kjellander_webrtc wrote:
> > > > Will run WebRTC tryjobs in PS#2.
> > > 
> > > The baremetal failure was caused by a stale test that is now removed.
> > 
> > Can you fire the swarming bots too, please?
> 
> Done, and they're green.

LGTM

[kjellander_webrtc, 2016-10-28 06:05:22]

Description was changed from

==========
GN: Add default target + refactorings

This CL assumes each GN target is one of 4 categories:
* Production code
* Tests
* Examples
* Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

A new convention is also introduced: Each directory's BUILD.gn file
shall contain a target named similar to the directroy name. This target
is supposed to contain the 'most common' production code, i.e. 
so that most consumers of the directory can depend on only the directory
(without specifying which target inside it they need).

//webrtc:webrtc_tests is changed to become a group that compiles
all WebRTC tests. A few more new group targets are created in directories
that contain multiple tests, to avoid having to list all in
//webrtc:webrtc_tests.

The 'root' target at the top level is renamed to 'default' and now depend on
everything we want to build. Having this, what's built is explicit instead of
building all generated GN targets (which adds a lot of unnecessary
objects to be compiled). This cuts down the number of compiled objects
on Android from 8855 to 6276.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

to

==========
GN: Add default target and new groups + refactorings

This CL assumes each GN target is one of 4 categories:
* Production code
* Tests
* Examples
* Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

A new convention is also introduced: Each directory's BUILD.gn file
shall contain a target named similar to the directory name. This target
is supposed to contain the 'most common' production code, i.e. 
so that most consumers of the directory can depend on only the directory
(without specifying which target inside it they need).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests. 

Two new group targets:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
are created to avoid having to list all targets in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid dependency cycles due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default' and now depend on
everything we want to build. Having this, what's built is explicit instead of
building all generated GN targets (which adds a lot of unnecessary
objects to be compiled). This cuts down the number of compiled objects
on Android from 8855 to 6276.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

[kjellander_webrtc, 2016-10-28 07:10:19]

Description was changed from

==========
GN: Add default target and new groups + refactorings

This CL assumes each GN target is one of 4 categories:
* Production code
* Tests
* Examples
* Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

A new convention is also introduced: Each directory's BUILD.gn file
shall contain a target named similar to the directory name. This target
is supposed to contain the 'most common' production code, i.e. 
so that most consumers of the directory can depend on only the directory
(without specifying which target inside it they need).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests. 

Two new group targets:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
are created to avoid having to list all targets in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid dependency cycles due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default' and now depend on
everything we want to build. Having this, what's built is explicit instead of
building all generated GN targets (which adds a lot of unnecessary
objects to be compiled). This cuts down the number of compiled objects
on Android from 8855 to 6276.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

to

==========
GN: Add default target and new groups + refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall 
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled. 

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#...).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to
6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

[kjellander_webrtc, 2016-10-28 07:12:38]

kjellander@webrtc.org changed reviewers:
+ henrik.lundin@webrtc.org

[kjellander_webrtc, 2016-10-28 07:12:38]

+henrik.lundin@ mostly FYI for the new group targets in
//webrtc/modules/audio_coding and //webrtc/modules/audio_processing.

I'll send an e-mail out to all@webrtc.org informing about the convention changes
in this CL.

[kjellander_webrtc, 2016-10-28 07:13:04]

Description was changed from

==========
GN: Add default target and new groups + refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall 
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled. 

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#...).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to
6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

to

==========
GN: New conventions, default target and refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall 
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled. 

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#...).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to
6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

[kjellander_webrtc, 2016-10-28 12:39:37]

The CQ bit was checked by kjellander@webrtc.org

[kjellander_webrtc, 2016-10-28 12:39:38]

The patchset sent to the CQ was uploaded after l-g-t-m from
ehmaldonado@webrtc.org
Link to the patchset: https://codereview.webrtc.org/2441383002/#ps160001 (title:
"Restored root BUILD.gn for submit.")

[commit-bot: I haz the power, 2016-10-28 12:39:50]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[kjellander_webrtc, 2016-10-28 12:41:59]

The CQ bit was unchecked by kjellander@webrtc.org

[kjellander_webrtc, 2016-10-28 12:42:10]

Description was changed from

==========
GN: New conventions, default target and refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall 
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled. 

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#...).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to
6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
==========

to

==========
GN: New conventions, default target and refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall 
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled. 

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#...).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to
6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
NOTRY=True
==========

[kjellander_webrtc, 2016-10-28 12:42:20]

The CQ bit was checked by kjellander@webrtc.org

[commit-bot: I haz the power, 2016-10-28 12:42:30]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2016-10-28 12:44:05]

Description was changed from

==========
GN: New conventions, default target and refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall 
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled. 

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#...).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to
6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
NOTRY=True
==========

to

==========
GN: New conventions, default target and refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall 
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled. 

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#...).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to
6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
NOTRY=True
==========

[commit-bot: I haz the power, 2016-10-28 12:44:06]

Committed patchset #8 (id:160001)

[commit-bot: I haz the power, 2016-10-28 12:44:09]

Description was changed from

==========
GN: New conventions, default target and refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree, 
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall 
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled. 

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic 
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#...).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to
6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
NOTRY=True
==========

to

==========
GN: New conventions, default target and refactorings

Introduce a convention on categorizing GN targets:
1. Production code
2. Tests
3. Examples
4. Tools
The first two have targets spread out all over the tree,
while the latter are isolated to examples/ and tools/ directories.

Another new convention: Each directory's BUILD.gn file shall contain
a target named similar to the directory name. This target shall
contain the 'most common' production code, i.e. so that most
consumers of the directory can depend on only the directory
(which implicitly means that target in GN).

//webrtc:webrtc_tests is changed to depend on all WebRTC tests.
From now on, it's necessary to add new test targets to this dependency
tree in order to get them compiled.

Two new group targets are created:
//webrtc/modules/audio_coding:audio_coding_tests
//webrtc/modules/audio_processing:audio_processing_tests
to reduce the long list of tests in //webrtc:webrtc_tests.

Visibility on //webrtc:webrtc and  //webrtc:webrtc_tests is restricted
to the root target, to avoid circular dependencies due to the monolithic
property of these targets (a problem we've had in the past).

The 'root' target at the top level is renamed to 'default', which means GN will
build this target instead of _all_ generated targets
(see
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/faq.md#...).
This target now depends on everything we want to build, meaning all targets now
explicitly needs to be wired up from the root target in order to get build.
Having this, the number of compiled objects on Android is decreased from 8855 to
6276. It also gives us better control over our build.

BUG=webrtc:6440
TESTED=git cl try --clobber
NOTRY=True

Committed: https://crrev.com/6ceab083225dfa485bb48f9e43231c216acccbaf
Cr-Commit-Position: refs/heads/master@{#14821}
==========

[commit-bot: I haz the power, 2016-10-28 12:44:11]

Patchset 8 (id:??) landed as
https://crrev.com/6ceab083225dfa485bb48f9e43231c216acccbaf
Cr-Commit-Position: refs/heads/master@{#14821}