Fix style guide issues in audio mixer.

This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on common.h)
5. Disallow constructor macros added.

NOTRY=true

Committed: https://crrev.com/a4c2106120e693d7e928454dfb1d26954d972e12
Cr-Commit-Position: refs/heads/master@{#14120}

[aleloi, 2016-08-31 12:24:21]

Description was changed from

==========
Small mixer changes TODO change title.


1. Use of const everywhere
2. Changed variables to match code style
3. Removed some stale comments.
4. Probably something else, TODO look through diff.
==========

to

==========
Small mixer changes TODO change title.


1. Use of const everywhere
2. Changed variables to match code style
3. Removed some stale comments.
4. Added chromium clang plugin check (now possible thanks to kwiberg@'s work on
common.h)
4. Probably something else, TODO look through diff.
==========

[aleloi, 2016-08-31 12:31:29]

Description was changed from

==========
Small mixer changes TODO change title.


1. Use of const everywhere
2. Changed variables to match code style
3. Removed some stale comments.
4. Added chromium clang plugin check (now possible thanks to kwiberg@'s work on
common.h)
4. Probably something else, TODO look through diff.
==========

to

==========
This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code
style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on
common.h)
5. Disallow constructor macros added.
==========

[aleloi, 2016-08-31 12:31:29]

aleloi@webrtc.org changed reviewers:
+ ivoc@webrtc.org, kwiberg@webrtc.org

[aleloi, 2016-08-31 12:35:05]

... and part 3/3 is uploaded! Please take a look at this one too!

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/BU...
File webrtc/modules/audio_mixer/BUILD.gn (left):

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/BU...
webrtc/modules/audio_mixer/BUILD.gn:40: 
Now that //webrtc/common.h is fixed by kwiberg@, I can enable the
clang warnings here.

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/au...
File webrtc/modules/audio_mixer/audio_mixer.h (left):

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/au...
webrtc/modules/audio_mixer/audio_mixer.h:31: kLowestPossible = -1,
Not used any longer.

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/au...
File webrtc/modules/audio_mixer/audio_mixer.h (right):

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/au...
webrtc/modules/audio_mixer/audio_mixer.h:74:
RTC_DISALLOW_COPY_AND_ASSIGN(AudioMixer);
Copying a mixer should be forbidden, as the mixer expects only it can
ask AudioSources for audio. There hasn't been any use case for
assignment.

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/au...
File webrtc/modules/audio_mixer/audio_mixer_impl.cc (left):

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/au...
webrtc/modules/audio_mixer/audio_mixer_impl.cc:198: std::map<int,
MixerAudioSource*> mixedAudioSourcesMap;
Isn't used any longer. Strange that this was unnoticed by the bots.

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/au...
File webrtc/modules/audio_mixer/audio_mixer_impl.h (left):

https://codereview.webrtc.org/2294263002/diff/1/webrtc/modules/audio_mixer/au...
webrtc/modules/audio_mixer/audio_mixer_impl.h:93: 
These two have not been used for the last 5-6 mixer changes.

[aleloi, 2016-08-31 15:43:28]

Patchset #3 (id:30001) has been deleted

[aleloi, 2016-08-31 15:45:32]

The CQ bit was checked by aleloi@webrtc.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-31 15:45:39]

Dry run: 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, 2016-08-31 17:46:26]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-31 17:46:27]

Dry run: Try jobs failed on following builders:
  android_arm64_rel on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_clang_dbg on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_clang_rel on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_dbg on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_drmemory_light on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_rel on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_x64_clang_dbg on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_x64_clang_rel on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_x64_dbg on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_x64_gyp_dbg on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_x64_gyp_rel on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)
  win_x64_rel on master.tryserver.webrtc (JOB_TIMED_OUT, no build URL)

[kwiberg-webrtc, 2016-09-01 11:59:11]

lgtm

https://codereview.webrtc.org/2294263002/diff/50001/webrtc/modules/audio_mixe...
File webrtc/modules/audio_mixer/audio_mixer_impl.cc (right):

https://codereview.webrtc.org/2294263002/diff/50001/webrtc/modules/audio_mixe...
webrtc/modules/audio_mixer/audio_mixer_impl.cc:103: delete mix_history_;
Could you use a unique_ptr instead of a raw pointer for this one?

https://codereview.webrtc.org/2294263002/diff/50001/webrtc/modules/audio_mixe...
webrtc/modules/audio_mixer/audio_mixer_impl.cc:363: for (const auto audio_source
: audio_source_list_) {
If it's a pointer type, readability is greatly improved if you write const auto*
instead of just const auto. Same with const auto&.

[aleloi, 2016-09-01 13:36:17]

https://codereview.webrtc.org/2294263002/diff/50001/webrtc/modules/audio_mixe...
File webrtc/modules/audio_mixer/audio_mixer_impl.cc (right):

https://codereview.webrtc.org/2294263002/diff/50001/webrtc/modules/audio_mixe...
webrtc/modules/audio_mixer/audio_mixer_impl.cc:103: delete mix_history_;
On 2016/09/01 11:59:11, kwiberg-webrtc wrote:
> Could you use a unique_ptr instead of a raw pointer for this one?

I'll do it in the dependent CL https://codereview.webrtc.org/2302483002/ because
I moved MixHistory to avoid forward declaration.

https://codereview.webrtc.org/2294263002/diff/50001/webrtc/modules/audio_mixe...
webrtc/modules/audio_mixer/audio_mixer_impl.cc:363: for (const auto audio_source
: audio_source_list_) {
On 2016/09/01 11:59:11, kwiberg-webrtc wrote:
> If it's a pointer type, readability is greatly improved if you write const
auto*
> instead of just const auto. Same with const auto&.

It's auto * const here since only the pointer is const. I think it's more clear
with auto * const.

[kwiberg-webrtc, 2016-09-01 19:46:33]

https://codereview.webrtc.org/2294263002/diff/50001/webrtc/modules/audio_mixe...
File webrtc/modules/audio_mixer/audio_mixer_impl.cc (right):

https://codereview.webrtc.org/2294263002/diff/50001/webrtc/modules/audio_mixe...
webrtc/modules/audio_mixer/audio_mixer_impl.cc:363: for (const auto audio_source
: audio_source_list_) {
On 2016/09/01 13:36:17, aleloi wrote:
> On 2016/09/01 11:59:11, kwiberg-webrtc wrote:
> > If it's a pointer type, readability is greatly improved if you write const
> auto*
> > instead of just const auto. Same with const auto&.
> 
> It's auto * const here since only the pointer is const. I think it's more
clear
> with auto * const.

Ah, right.

[ivoc, 2016-09-07 11:33:45]

lgtm, sorry for the delay. See one remark below.

https://codereview.webrtc.org/2294263002/diff/150001/webrtc/modules/audio_mix...
File webrtc/modules/audio_mixer/audio_mixer_impl.cc (right):

https://codereview.webrtc.org/2294263002/diff/150001/webrtc/modules/audio_mix...
webrtc/modules/audio_mixer/audio_mixer_impl.cc:104: delete mix_history_;
How about changing mix_history into a unique_ptr?

[aleloi, 2016-09-07 11:38:11]

https://codereview.webrtc.org/2294263002/diff/150001/webrtc/modules/audio_mix...
File webrtc/modules/audio_mixer/audio_mixer_impl.cc (right):

https://codereview.webrtc.org/2294263002/diff/150001/webrtc/modules/audio_mix...
webrtc/modules/audio_mixer/audio_mixer_impl.cc:104: delete mix_history_;
On 2016/09/07 11:33:45, ivoc wrote:
> How about changing mix_history into a unique_ptr?

Fixed in one of the dependent CLs https://codereview.webrtc.org/2302483002

[aleloi, 2016-09-07 15:39:23]

The CQ bit was checked by aleloi@webrtc.org

[aleloi, 2016-09-07 15:39:24]

The patchset sent to the CQ was uploaded after l-g-t-m from kwiberg@webrtc.org
Link to the patchset: https://codereview.webrtc.org/2294263002/#ps150001 (title:
"Rebase.")

[commit-bot: I haz the power, 2016-09-07 15:39:30]

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, 2016-09-07 15:50:04]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-09-07 15:50:05]

Try jobs failed on following builders:
  android_arm64_rel on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/android_arm64_rel/build...)

[aleloi, 2016-09-08 08:17:27]

Description was changed from

==========
This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code
style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on
common.h)
5. Disallow constructor macros added.
==========

to

==========
This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code
style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on
common.h)
5. Disallow constructor macros added.

NOTRY=True
==========

[aleloi, 2016-09-08 08:17:42]

Description was changed from

==========
This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code
style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on
common.h)
5. Disallow constructor macros added.

NOTRY=True
==========

to

==========
This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code
style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on
common.h)
5. Disallow constructor macros added.

NOTRY=true
==========

[aleloi, 2016-09-08 08:17:47]

The CQ bit was checked by aleloi@webrtc.org

[commit-bot: I haz the power, 2016-09-08 08:17:51]

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, 2016-09-08 08:25:48]

Description was changed from

==========
This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code
style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on
common.h)
5. Disallow constructor macros added.

NOTRY=true
==========

to

==========
This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code
style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on
common.h)
5. Disallow constructor macros added.

NOTRY=true
==========

[commit-bot: I haz the power, 2016-09-08 08:25:49]

Committed patchset #8 (id:150001)

[commit-bot: I haz the power, 2016-09-08 08:25:59]

Description was changed from

==========
This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code
style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on
common.h)
5. Disallow constructor macros added.

NOTRY=true
==========

to

==========
This CL contains the following small changes:

1. Use of const in all variable declarations where it is possible
2. Variable names and function arguments changed from CamelCase to match code
style
3. A few stale comments removed.
4. Chromium clang plugin check added (now possible thanks to kwiberg@'s work on
common.h)
5. Disallow constructor macros added.

NOTRY=true

Committed: https://crrev.com/a4c2106120e693d7e928454dfb1d26954d972e12
Cr-Commit-Position: refs/heads/master@{#14120}
==========

[commit-bot: I haz the power, 2016-09-08 08:26:00]

Patchset 8 (id:??) landed as
https://crrev.com/a4c2106120e693d7e928454dfb1d26954d972e12
Cr-Commit-Position: refs/heads/master@{#14120}