[Chromecast] Initialize media_resource_tracker with media_thread.

[Chromecast] Initialize media_resource_tracker with media_thread.

There was a race condition with the lazy initialization logic
from before, where the media_resource_tracker() lazy-getter
could be called by something on the media thread before the
call to media_resource_tracker()->InitializeMediaLib() in
cast_browser_main_parts. This would make the media resource
tracker think that the media thread was the UI thread, which
would cause the InitializeMediaLib() call to fail, thinking
it was on the wrong thread.

BUG=NONE
TEST=build cast_shell_apk with gn arg
     is_cast_audio_only=true, install on Android emulator
     and verify that crash does not happen on browser process
     startup.

Review-Url: https://codereview.chromium.org/2811293003
Cr-Commit-Position: refs/heads/master@{#464297}
Committed: https://chromium.googlesource.com/chromium/src/+/ebc15025d19fb3a0be141495f36f36b5cd73673e

[Simeon, 2017-04-12 23:48:47]

sanfin@chromium.org changed reviewers:
+ halliwell@chromium.org

[Simeon, 2017-04-12 23:48:47]

This fixes the crash that thoren@ and I were seeing yesterday on Android
emulators.

[halliwell, 2017-04-13 00:49:04]

On 2017/04/12 23:48:47, Simeon wrote:
> This fixes the crash that thoren@ and I were seeing yesterday on Android
> emulators.

lgtm

[Simeon, 2017-04-13 04:09:11]

The CQ bit was checked by sanfin@chromium.org

[commit-bot: I haz the power, 2017-04-13 04:09:38]

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, 2017-04-13 04:43:14]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1492056551067470, "parent_rev":
"d0605bc9ca32f07f098363e0b1dc7d5a9bc075e8", "commit_rev":
"ebc15025d19fb3a0be141495f36f36b5cd73673e"}

[commit-bot: I haz the power, 2017-04-13 04:44:55]

Description was changed from

==========
[Chromecast] Initialize media_resource_tracker with media_thread.

There was a race condition with the lazy initialization logic
from before, where the media_resource_tracker() lazy-getter
could be called by something on the media thread before the
call to media_resource_tracker()->InitializeMediaLib() in
cast_browser_main_parts. This would make the media resource
tracker think that the media thread was the UI thread, which
would cause the InitializeMediaLib() call to fail, thinking
it was on the wrong thread.

BUG=NONE
TEST=build cast_shell_apk with gn arg
     is_cast_audio_only=true, install on Android emulator
     and verify that crash does not happen on browser process
     startup.
==========

to

==========
[Chromecast] Initialize media_resource_tracker with media_thread.

There was a race condition with the lazy initialization logic
from before, where the media_resource_tracker() lazy-getter
could be called by something on the media thread before the
call to media_resource_tracker()->InitializeMediaLib() in
cast_browser_main_parts. This would make the media resource
tracker think that the media thread was the UI thread, which
would cause the InitializeMediaLib() call to fail, thinking
it was on the wrong thread.

BUG=NONE
TEST=build cast_shell_apk with gn arg
     is_cast_audio_only=true, install on Android emulator
     and verify that crash does not happen on browser process
     startup.

Review-Url: https://codereview.chromium.org/2811293003
Cr-Commit-Position: refs/heads/master@{#464297}
Committed:
https://chromium.googlesource.com/chromium/src/+/ebc15025d19fb3a0be141495f36f...
==========

[commit-bot: I haz the power, 2017-04-13 04:44:56]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/ebc15025d19fb3a0be141495f36f...