Revert of Remove MediaStreamTrack.getSources().

Revert of Remove MediaStreamTrack.getSources(). (patchset #4 id:80001 of https://codereview.chromium.org/2471803002/ )

Reason for revert:
Broke some test metrics. See http://crbug.com/662414.

Original issue's description:
> Remove MediaStreamTrack.getSources().
> 
> Intent-to-remove thread:
> https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/do3t86PtHCY
> 
> BUG=649710, 388194
> 
> Committed: https://crrev.com/3ea42b21339ebf028e0ff6e368ca60d463386dd2
> Cr-Commit-Position: refs/heads/master@{#429745}

TBR=rbyers@chromium.org,hbos@chromium.org,guidou@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=649710, 388194

[brianderson, 2016-11-08 22:27:25]

The CQ bit was checked by brianderson@chromium.org

[brianderson, 2016-11-08 22:27:25]

Created Revert of Remove MediaStreamTrack.getSources().

[commit-bot: I haz the power, 2016-11-08 22:28:13]

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

[commit-bot: I haz the power, 2016-11-08 22:33:33]

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

[commit-bot: I haz the power, 2016-11-08 22:33:34]

Try jobs failed on following builders:
  android_compile_dbg on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_comp...)
  android_n5x_swarming_rel on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_n5x_...)
  cast_shell_android on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/cast_shell_a...)
  chromeos_x86-generic_chromium_compile_only_ng on
master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_x86-ge...)
  linux_chromium_chromeos_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  ios-device on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device/builds...)
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)
  mac_chromium_compile_dbg_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[brianderson, 2016-11-08 22:50:21]

Description was changed from

==========
Revert of Remove MediaStreamTrack.getSources(). (patchset #4 id:80001 of
https://codereview.chromium.org/2471803002/ )

Reason for revert:
Broke some test metrics. See http://crbug.com/662414.

Original issue's description:
> Remove MediaStreamTrack.getSources().
> 
> Intent-to-remove thread:
> https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/do3t86PtHCY
> 
> BUG=649710,388194
> 
> Committed: https://crrev.com/3ea42b21339ebf028e0ff6e368ca60d463386dd2
> Cr-Commit-Position: refs/heads/master@{#429745}

TBR=rbyers@chromium.org,hbos@chromium.org,guidou@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=649710,388194
==========

to

==========
Revert of Remove MediaStreamTrack.getSources(). (patchset #4 id:80001 of
https://codereview.chromium.org/2471803002/ )

Reason for revert:
Broke some test metrics. See http://crbug.com/662414.

Original issue's description:
> Remove MediaStreamTrack.getSources().
> 
> Intent-to-remove thread:
> https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/do3t86PtHCY
> 
> BUG=649710,388194
> 
> Committed: https://crrev.com/3ea42b21339ebf028e0ff6e368ca60d463386dd2
> Cr-Commit-Position: refs/heads/master@{#429745}

TBR=rbyers@chromium.org,hbos@chromium.org,guidou@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=649710,388194
==========