Fix a bug when using gtest-parallel on swarming (plus flag related changes).

Fixed a bug where only the tests in the first shard were run.

This is because:
1) The environment variables were still around when the test was executed.
2) gtest-parallel executes only one test at a time.

So when the test was invoked from a shard different than the 0th one, for example as:
./something_unittests --gtest_filter=Test.Name
It read the environment variables, and the environment variables together with the gtest_filter flag, told it that there were several shards, but only one test to be run, so if it wasn't the 0th shard, it wouldn't run the test at all.

This is fixed by erasing the environment variables once read.

Also change swarming-related flag names to fit the rest of the flags and validate their values.

NOTRY=True
BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org

Committed: https://crrev.com/aee0b5d31737f476e5c3ea2eb34e00a6f101caea
Cr-Commit-Position: refs/heads/master@{#15110}

[ehmaldonado_webrtc, 2016-11-16 21:17:46]

https://codereview.webrtc.org/2505093003/diff/1/third_party/gtest-parallel/gt...
File third_party/gtest-parallel/gtest-parallel (right):

https://codereview.webrtc.org/2505093003/diff/1/third_party/gtest-parallel/gt...
third_party/gtest-parallel/gtest-parallel:269:
parser.add_option('--shard_count', type='int',
I decided to leave it as 'int' to keep it the same as the -r and -w flags above.

[ehmaldonado_webrtc, 2016-11-17 00:10:45]

Description was changed from

==========
Change swarming-related flag names and validate their values.

BUG=chromium:497757, chromium:664425
R=pbos@webrtc.org
==========

to

==========
Fixed a bug where only the tests in the first shard were run.

This is because the environment variables were still around when the test was
executed.
Since gtest-parallel executes only one test at a time, if we're not in the first
shard, the test is skipped by the test binary (i.e. modules_unittests) since it
now thinks that is being asked to execute just one test, and the first shard
should take care of it.

Also change swarming-related flag names to fit the rest of the flags and
validate their values.

BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org
==========

[ehmaldonado_webrtc, 2016-11-17 00:14:35]

Patchset #2 (id:20001) has been deleted

[ehmaldonado_webrtc, 2016-11-17 00:17:53]

Patchset #3 (id:60001) has been deleted

[ehmaldonado_webrtc, 2016-11-17 00:25:26]

Description was changed from

==========
Fixed a bug where only the tests in the first shard were run.

This is because the environment variables were still around when the test was
executed.
Since gtest-parallel executes only one test at a time, if we're not in the first
shard, the test is skipped by the test binary (i.e. modules_unittests) since it
now thinks that is being asked to execute just one test, and the first shard
should take care of it.

Also change swarming-related flag names to fit the rest of the flags and
validate their values.

BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org
==========

to

==========
Fixed a bug where only the tests in the first shard were run.

This is because: 
1) The environment variables were still around when the test was executed.
2) gtest-parallel executes only one test at a time.

So when the test was invoked from a shard different than the 0th one, for
example as:
./something_unittests --gtest_filter=Test.Name
It read the environment variables, and the environment variables together with
the gtest_filter flag, told it that there were several shards, but only one test
to be run, so if it wasn't the 0th shard, it wouldn't run the test at all.

This is fixed by erasing the environment variables once read.

Also change swarming-related flag names to fit the rest of the flags and
validate their values.

BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org
==========

[ehmaldonado_webrtc, 2016-11-17 00:27:44]

The CQ bit was checked by ehmaldonado@webrtc.org

[commit-bot: I haz the power, 2016-11-17 00:27:55]

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

[ehmaldonado_webrtc, 2016-11-17 00:29:10]

The CQ bit was unchecked by ehmaldonado@webrtc.org

[ehmaldonado_webrtc, 2016-11-17 00:29:17]

The CQ bit was checked by ehmaldonado@webrtc.org

[ehmaldonado_webrtc, 2016-11-17 00:29:18]

The CQ bit was unchecked by ehmaldonado@webrtc.org

[ehmaldonado_webrtc, 2016-11-17 00:29:20]

The CQ bit was checked by ehmaldonado@webrtc.org

[commit-bot: I haz the power, 2016-11-17 00:29:24]

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, 2016-11-17 00:32:21]

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

[commit-bot: I haz the power, 2016-11-17 00:32:22]

Try jobs failed on following builders:
  linux_ubsan on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/linux_ubsan/builds/6891)
  win_baremetal on master.tryserver.webrtc (JOB_FAILED,
http://build.chromium.org/p/tryserver.webrtc/builders/win_baremetal/builds/16193)

[ehmaldonado_webrtc, 2016-11-17 00:41:32]

Description was changed from

==========
Fixed a bug where only the tests in the first shard were run.

This is because: 
1) The environment variables were still around when the test was executed.
2) gtest-parallel executes only one test at a time.

So when the test was invoked from a shard different than the 0th one, for
example as:
./something_unittests --gtest_filter=Test.Name
It read the environment variables, and the environment variables together with
the gtest_filter flag, told it that there were several shards, but only one test
to be run, so if it wasn't the 0th shard, it wouldn't run the test at all.

This is fixed by erasing the environment variables once read.

Also change swarming-related flag names to fit the rest of the flags and
validate their values.

BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org
==========

to

==========
Fixed a bug where only the tests in the first shard were run.

This is because: 
1) The environment variables were still around when the test was executed.
2) gtest-parallel executes only one test at a time.

So when the test was invoked from a shard different than the 0th one, for
example as:
./something_unittests --gtest_filter=Test.Name
It read the environment variables, and the environment variables together with
the gtest_filter flag, told it that there were several shards, but only one test
to be run, so if it wasn't the 0th shard, it wouldn't run the test at all.

This is fixed by erasing the environment variables once read.

Also change swarming-related flag names to fit the rest of the flags and
validate their values.

NOTRY=True
BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org
==========

[ehmaldonado_webrtc, 2016-11-17 00:45:27]

The CQ bit was checked by ehmaldonado@webrtc.org

[commit-bot: I haz the power, 2016-11-17 00:45:32]

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, 2016-11-17 00:48:15]

Description was changed from

==========
Fixed a bug where only the tests in the first shard were run.

This is because: 
1) The environment variables were still around when the test was executed.
2) gtest-parallel executes only one test at a time.

So when the test was invoked from a shard different than the 0th one, for
example as:
./something_unittests --gtest_filter=Test.Name
It read the environment variables, and the environment variables together with
the gtest_filter flag, told it that there were several shards, but only one test
to be run, so if it wasn't the 0th shard, it wouldn't run the test at all.

This is fixed by erasing the environment variables once read.

Also change swarming-related flag names to fit the rest of the flags and
validate their values.

NOTRY=True
BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org
==========

to

==========
Fixed a bug where only the tests in the first shard were run.

This is because: 
1) The environment variables were still around when the test was executed.
2) gtest-parallel executes only one test at a time.

So when the test was invoked from a shard different than the 0th one, for
example as:
./something_unittests --gtest_filter=Test.Name
It read the environment variables, and the environment variables together with
the gtest_filter flag, told it that there were several shards, but only one test
to be run, so if it wasn't the 0th shard, it wouldn't run the test at all.

This is fixed by erasing the environment variables once read.

Also change swarming-related flag names to fit the rest of the flags and
validate their values.

NOTRY=True
BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org
==========

[commit-bot: I haz the power, 2016-11-17 00:48:16]

Committed patchset #2 (id:40001)

[commit-bot: I haz the power, 2016-11-17 00:48:19]

Description was changed from

==========
Fixed a bug where only the tests in the first shard were run.

This is because: 
1) The environment variables were still around when the test was executed.
2) gtest-parallel executes only one test at a time.

So when the test was invoked from a shard different than the 0th one, for
example as:
./something_unittests --gtest_filter=Test.Name
It read the environment variables, and the environment variables together with
the gtest_filter flag, told it that there were several shards, but only one test
to be run, so if it wasn't the 0th shard, it wouldn't run the test at all.

This is fixed by erasing the environment variables once read.

Also change swarming-related flag names to fit the rest of the flags and
validate their values.

NOTRY=True
BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org
==========

to

==========
Fixed a bug where only the tests in the first shard were run.

This is because:
1) The environment variables were still around when the test was executed.
2) gtest-parallel executes only one test at a time.

So when the test was invoked from a shard different than the 0th one, for
example as:
./something_unittests --gtest_filter=Test.Name
It read the environment variables, and the environment variables together with
the gtest_filter flag, told it that there were several shards, but only one test
to be run, so if it wasn't the 0th shard, it wouldn't run the test at all.

This is fixed by erasing the environment variables once read.

Also change swarming-related flag names to fit the rest of the flags and
validate their values.

NOTRY=True
BUG=chromium:497757, chromium:664425
TBR=pbos@webrtc.org, kjellander@webrtc.org

Committed: https://crrev.com/aee0b5d31737f476e5c3ea2eb34e00a6f101caea
Cr-Commit-Position: refs/heads/master@{#15110}
==========

[commit-bot: I haz the power, 2016-11-17 00:48:20]

Patchset 2 (id:??) landed as
https://crrev.com/aee0b5d31737f476e5c3ea2eb34e00a6f101caea
Cr-Commit-Position: refs/heads/master@{#15110}