WebRTCPeerConnectionHandler::getStats for the new stats collector API

WebRTCPeerConnectionHandler::getStats for the new stats collector API.

Adds a new getStats, implemented by RTCPeerConnectionHandler. This is a
part of surfacing the new stats collection API from WebRTC to Blink. In
follow-up CLs the blink::RTCPeerConnection will begin to use it. The old
stats collection API will be kept until the new API has matured.

Main changes:
- MockWebRTCPeerConnectionHandler interface gets a new getStats.
  RTCPeerConnectionHandler implements it, calling the
  webrtc::PeerConnectionInterface's getStats. This involves jumping from
  main thread to signaling thread and back to main thread in a callback.
  The resulting webrtc::RTCStatsReport is surfaced to Blink using a
  content::RTCStatsReport.
- The callback to Blink is performed using the new interface
  blink::WebRTCStatsReportCallback.
- WebRTCStatsMember gets an isDefined function, implemented by
  content::RTCStatsMember.

Test changes:
- MockPeerConnectionImpl implements webrtc::PeerConnectionInterface's
  getStats to return a specified webrtc::RTCStatsReport.
- rtc_peer_connection_handler_test.cc tests RTCPeerConnectionHandler's
  getStats. The test confirms that we get the expected Blink layer stats
  by mocking the WebRTC peer connection to return a stats object defined
  in the test.

BUG=chromium:627816
Committed: https://crrev.com/9f64bf32920b4dd5e0eecd59f45b46208a002fd1
Cr-Commit-Position: refs/heads/master@{#420837}

[hbos_chromium, 2016-09-08 12:47:57]

Patchset #1 (id:1) has been deleted

[hbos_chromium, 2016-09-14 12:13:47]

Patchset #1 (id:20001) has been deleted

[hbos_chromium, 2016-09-19 11:25:56]

Patchset #1 (id:40001) has been deleted

[hbos_chromium, 2016-09-19 11:26:05]

Patchset #1 (id:60001) has been deleted

[hbos_chromium, 2016-09-19 11:27:01]

The CQ bit was checked by hbos@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-19 11:27:18]

Dry run: 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, 2016-09-19 11:30:47]

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

[commit-bot: I haz the power, 2016-09-19 11:30:48]

Dry run: Try jobs failed on following builders:
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)
  linux_chromium_chromeos_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  linux_chromium_clobber_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  linux_chromium_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[hbos_chromium, 2016-09-19 14:09:07]

The CQ bit was checked by hbos@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-19 14:09:24]

Dry run: 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, 2016-09-19 16:20:51]

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

[commit-bot: I haz the power, 2016-09-19 16:20:52]

Dry run: Try jobs failed on following builders:
  win_chromium_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[hbos_chromium, 2016-09-20 09:02:09]

The CQ bit was checked by hbos@chromium.org to run a CQ dry run

[hbos_chromium, 2016-09-20 09:02:14]

Patchset #3 (id:120001) has been deleted

[hbos_chromium, 2016-09-20 09:02:20]

Patchset #2 (id:100001) has been deleted

[commit-bot: I haz the power, 2016-09-20 09:02:27]

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

[hbos_chromium, 2016-09-20 09:02:29]

Patchset #1 (id:80001) has been deleted

[hbos_chromium, 2016-09-20 09:38:38]

The CQ bit was checked by hbos@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-20 09:38:56]

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

[hbos_chromium, 2016-09-20 10:01:34]

Description was changed from

==========
RTCPeerConnectionHandler new GetStats using new stats collection API.

BUG=chromium:627816
==========

to

==========
WebRTCPeerConnectionHandler::getStats for the new stats collector API.

Adds a new getStats, implemented by RTCPeerConnectionHandler. This is a
part of surfacing the new stats collection API from WebRTC to Blink. In
follow-up CLs the blink::RTCPeerConnection will begin to use it. The old
stats collection API will be kept until the new API has matured.

Main changes:
- MockWebRTCPeerConnectionHandler interface gets a new getStats.
  RTCPeerConnectionHandler implements it, calling the
  webrtc::PeerConnectionInterface's getStats. This involves jumping from
  main thread to signaling thread and back to main thread in a callback.
  The resulting webrtc::RTCStatsReport is surfaced to Blink using a
  content::RTCStatsReport.
- The callback to Blink is performed using the new interface
  blink::WebRTCStatsReportCallback.
- WebRTCStatsMember gets an isDefined function, implemented by
  content::RTCStatsMember.

Test util class changes:
- MockWebRTCPeerConnectionHandler implements the new getStats by
  defining a set of MockRTCStats... classes. This will be used in
  follow-up CLs when RTCPeerConnection starts using the new getStats.
- MockPeerConnectionImpl implements webrtc::PeerConnectionInterface's
  getStats to return a specified webrtc::RTCStatsReport.

Tests:
- rtc_peer_connection_handler_test.cc tests RTCPeerConnectionHandler's
  getStats. The test confirms that we get the corresponding Blink layer
  stats by mocking the WebRTC peer connection to return a stats object
  defined in the test.

BUG=chromium:627816
==========

[hbos_chromium, 2016-09-20 10:23:30]

The CQ bit was checked by hbos@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-20 10:23:37]

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

[hbos_chromium, 2016-09-20 10:30:38]

Description was changed from

==========
WebRTCPeerConnectionHandler::getStats for the new stats collector API.

Adds a new getStats, implemented by RTCPeerConnectionHandler. This is a
part of surfacing the new stats collection API from WebRTC to Blink. In
follow-up CLs the blink::RTCPeerConnection will begin to use it. The old
stats collection API will be kept until the new API has matured.

Main changes:
- MockWebRTCPeerConnectionHandler interface gets a new getStats.
  RTCPeerConnectionHandler implements it, calling the
  webrtc::PeerConnectionInterface's getStats. This involves jumping from
  main thread to signaling thread and back to main thread in a callback.
  The resulting webrtc::RTCStatsReport is surfaced to Blink using a
  content::RTCStatsReport.
- The callback to Blink is performed using the new interface
  blink::WebRTCStatsReportCallback.
- WebRTCStatsMember gets an isDefined function, implemented by
  content::RTCStatsMember.

Test util class changes:
- MockWebRTCPeerConnectionHandler implements the new getStats by
  defining a set of MockRTCStats... classes. This will be used in
  follow-up CLs when RTCPeerConnection starts using the new getStats.
- MockPeerConnectionImpl implements webrtc::PeerConnectionInterface's
  getStats to return a specified webrtc::RTCStatsReport.

Tests:
- rtc_peer_connection_handler_test.cc tests RTCPeerConnectionHandler's
  getStats. The test confirms that we get the corresponding Blink layer
  stats by mocking the WebRTC peer connection to return a stats object
  defined in the test.

BUG=chromium:627816
==========

to

==========
WebRTCPeerConnectionHandler::getStats for the new stats collector API.

Adds a new getStats, implemented by RTCPeerConnectionHandler. This is a
part of surfacing the new stats collection API from WebRTC to Blink. In
follow-up CLs the blink::RTCPeerConnection will begin to use it. The old
stats collection API will be kept until the new API has matured.

Main changes:
- MockWebRTCPeerConnectionHandler interface gets a new getStats.
  RTCPeerConnectionHandler implements it, calling the
  webrtc::PeerConnectionInterface's getStats. This involves jumping from
  main thread to signaling thread and back to main thread in a callback.
  The resulting webrtc::RTCStatsReport is surfaced to Blink using a
  content::RTCStatsReport.
- The callback to Blink is performed using the new interface
  blink::WebRTCStatsReportCallback.
- WebRTCStatsMember gets an isDefined function, implemented by
  content::RTCStatsMember.

Test changes:
- MockPeerConnectionImpl implements webrtc::PeerConnectionInterface's
  getStats to return a specified webrtc::RTCStatsReport.
- rtc_peer_connection_handler_test.cc tests RTCPeerConnectionHandler's
  getStats. The test confirms that we get the expected Blink layer stats
  by mocking the WebRTC peer connection to return a stats object defined
  in the test.

BUG=chromium:627816
==========

[hbos_chromium, 2016-09-20 10:31:26]

hbos@chromium.org changed reviewers:
+ perkj@chromium.org, pfeldman@chromium.org

[hbos_chromium, 2016-09-20 10:31:27]

Please take a look, pfeldman and perkj.

[commit-bot: I haz the power, 2016-09-20 12:14:02]

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

[commit-bot: I haz the power, 2016-09-20 12:14:03]

Dry run: This issue passed the CQ dry run.

[hbos_chromium, 2016-09-20 12:57:51]

hbos@chromium.org changed reviewers:
+ foolip@chromium.org

[hbos_chromium, 2016-09-20 12:57:52]

Please take a look, foolip.

[foolip, 2016-09-20 14:21:49]

third_party/WebKit/ LGTM, didn't look closely elsewhere

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
File content/renderer/media/mock_peer_connection_impl.h (right):

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
content/renderer/media/mock_peer_connection_impl.h:47: // Set Call this function
to make sure next call to legacy GetStats fail.
Some weird typo here you might want to fix.

[hbos_chromium, 2016-09-20 14:25:35]

hbos@chromium.org changed reviewers:
+ hta@chromium.org

[hbos_chromium, 2016-09-20 14:25:36]

Can you take a look, hta?

[hta - Chromium, 2016-09-20 16:26:46]

lgtm

it's mostly framework so far.
Some comments.

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
File content/renderer/media/rtc_peer_connection_handler.cc (right):

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler.cc:677: // A stats collector
callback that is invoked on the WebRTC signaling thread and
Style: This sentence is quite hard to read.

Suggestion:

A stats collector callback.
It is invoked on the WebRTC signaling thread and will post a task to invoke
|callback| on the thread given in the |main_thread| argument.
The argument to the callback will be a |blink::WebRTCStatsReport|.

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
File content/renderer/media/rtc_peer_connection_handler_unittest.cc (right):

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler_unittest.cc:718: uint32_t
members_bitmap = 0x0;
This is a test, so readability is more important than speed.

I suggest you use a std::set<int> instead.
Perhaps even std::set<blink::WebRTCStatsMemberType> would work, in which case
you can set the set member outside of the switch, making the whole thing shorter
by 12 lines?

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler_unittest.cc:781:
EXPECT_EQ(members_bitmap, static_cast<uint32_t>(0xFFF));
With a set, you can just expect the number of members of the set to be 12.

[hbos_chromium, 2016-09-20 20:17:46]

The CQ bit was checked by hbos@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-20 20:18:12]

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

[hbos_chromium, 2016-09-20 20:18:39]

Please take a look, pfeldman and perkj.

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
File content/renderer/media/mock_peer_connection_impl.h (right):

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
content/renderer/media/mock_peer_connection_impl.h:47: // Set Call this function
to make sure next call to legacy GetStats fail.
On 2016/09/20 14:21:48, foolip wrote:
> Some weird typo here you might want to fix.

Done.

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
File content/renderer/media/rtc_peer_connection_handler.cc (right):

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler.cc:677: // A stats collector
callback that is invoked on the WebRTC signaling thread and
On 2016/09/20 16:26:45, hta - Chromium wrote:
> Style: This sentence is quite hard to read.
> 
> Suggestion:
> 
> A stats collector callback.
> It is invoked on the WebRTC signaling thread and will post a task to invoke
> |callback| on the thread given in the |main_thread| argument.
> The argument to the callback will be a |blink::WebRTCStatsReport|.

Done.

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
File content/renderer/media/rtc_peer_connection_handler_unittest.cc (right):

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler_unittest.cc:718: uint32_t
members_bitmap = 0x0;
On 2016/09/20 16:26:46, hta - Chromium wrote:
> This is a test, so readability is more important than speed.
> 
> I suggest you use a std::set<int> instead.
> Perhaps even std::set<blink::WebRTCStatsMemberType> would work, in which case
> you can set the set member outside of the switch, making the whole thing
shorter
> by 12 lines?
> 
> 

Good idea! Done.

https://codereview.chromium.org/2317063002/diff/180001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler_unittest.cc:781:
EXPECT_EQ(members_bitmap, static_cast<uint32_t>(0xFFF));
On 2016/09/20 16:26:45, hta - Chromium wrote:
> With a set, you can just expect the number of members of the set to be 12.

Done.

[commit-bot: I haz the power, 2016-09-20 21:42:59]

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

[commit-bot: I haz the power, 2016-09-20 21:43:00]

Dry run: This issue passed the CQ dry run.

[perkj_chrome, 2016-09-21 12:21:34]

lgtm with the comment below addressed.

https://codereview.chromium.org/2317063002/diff/200001/content/renderer/media...
File content/renderer/media/rtc_peer_connection_handler.cc (right):

https://codereview.chromium.org/2317063002/diff/200001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler.cc:688: main_thread,
callback.release()));
std::move - avoid using raw pointer.

https://codereview.chromium.org/2317063002/diff/200001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler.cc:709:
blink::WebRTCStatsReportCallback* callback)
std::unique_ptr<blink::WebRTCStatsReportCallback> callback and use std::move
above instead of release

[hbos_chromium, 2016-09-21 19:05:21]

Please take a look pfeldman

https://codereview.chromium.org/2317063002/diff/200001/content/renderer/media...
File content/renderer/media/rtc_peer_connection_handler.cc (right):

https://codereview.chromium.org/2317063002/diff/200001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler.cc:688: main_thread,
callback.release()));
On 2016/09/21 12:21:33, perkj_chrome wrote:
> std::move - avoid using raw pointer.

RefCountedObject's template constructors does not allow things which has to be
passed with std::move, it will attempt to copy the argument which is not allowed
by std::unique_ptr.

https://codereview.chromium.org/2317063002/diff/200001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler.cc:709:
blink::WebRTCStatsReportCallback* callback)
On 2016/09/21 12:21:33, perkj_chrome wrote:
> std::unique_ptr<blink::WebRTCStatsReportCallback> callback and use std::move
> above instead of release

See above.

[perkj_chrome, 2016-09-22 05:37:51]

https://codereview.chromium.org/2317063002/diff/200001/content/renderer/media...
File content/renderer/media/rtc_peer_connection_handler.cc (right):

https://codereview.chromium.org/2317063002/diff/200001/content/renderer/media...
content/renderer/media/rtc_peer_connection_handler.cc:688: main_thread,
callback.release()));
On 2016/09/21 19:05:21, hbos_chromium wrote:
> On 2016/09/21 12:21:33, perkj_chrome wrote:
> > std::move - avoid using raw pointer.
> 
> RefCountedObject's template constructors does not allow things which has to be
> passed with std::move, it will attempt to copy the argument which is not
allowed
> by std::unique_ptr.

I see, that should be fixed.

[hbos_chromium, 2016-09-22 18:20:24]

Please take a look pfeldman.

[hbos_chromium, 2016-09-23 08:07:32]

hbos@chromium.org changed reviewers:
+ blundell@chromium.org

[hbos_chromium, 2016-09-23 08:07:32]

Please take a look, blundell, for these files:
components/test_runner/mock_webrtc_peer_connection_handler.[h/cc]

[blundell, 2016-09-23 08:19:16]

lgtm

[hbos_chromium, 2016-09-23 08:27:41]

Patchset #5 (id:220001) has been deleted

[hbos_chromium, 2016-09-23 08:29:45]

hbos@chromium.org changed reviewers:
+ tommi@chromium.org

[hbos_chromium, 2016-09-23 08:29:46]

PTAL tommi for content/test/BUILD.gn

https://codereview.chromium.org/2317063002/diff/200001/content/test/BUILD.gn
File content/test/BUILD.gn (right):

https://codereview.chromium.org/2317063002/diff/200001/content/test/BUILD.gn#...
content/test/BUILD.gn:305: "//third_party/webrtc/stats:rtc_stats",
Because mock_peer_connection_impl.h includes
third_party/webrtc/api/stats/rtcstatsreport.h.

https://codereview.chromium.org/2317063002/diff/200001/content/test/BUILD.gn#...
content/test/BUILD.gn:1512: "//third_party/webrtc/stats:rtc_stats_test_utils",
Because rtc_peer_connection_handler_unittest.cc includes
third_party/webrtc/stats/test/rtcteststats.h

[tommi (sloooow) - chröme, 2016-09-23 08:32:41]

lgtm

[hbos_chromium, 2016-09-23 08:35:58]

The CQ bit was checked by hbos@chromium.org

[hbos_chromium, 2016-09-23 08:35:59]

The patchset sent to the CQ was uploaded after l-g-t-m from hta@chromium.org,
foolip@chromium.org
Link to the patchset: https://codereview.chromium.org/2317063002/#ps200001
(title: "Addressed comments")

[commit-bot: I haz the power, 2016-09-23 08:36:15]

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, 2016-09-23 09:25:56]

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

[commit-bot: I haz the power, 2016-09-23 09:25:57]

Try jobs failed on following builders:
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)

[hbos_chromium, 2016-09-23 09:27:14]

The CQ bit was checked by hbos@chromium.org

[commit-bot: I haz the power, 2016-09-23 09:27:31]

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, 2016-09-23 09:44:57]

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

[commit-bot: I haz the power, 2016-09-23 09:44:59]

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

[hbos_chromium, 2016-09-23 09:54:28]

The CQ bit was checked by hbos@chromium.org

[commit-bot: I haz the power, 2016-09-23 09:54:49]

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, 2016-09-23 11:02:48]

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

[commit-bot: I haz the power, 2016-09-23 11:02:49]

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

[hbos_chromium, 2016-09-23 13:35:44]

On 2016/09/23 11:02:49, commit-bot: I haz the power wrote:
> Try jobs failed on following builders:
>   win_chromium_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
>
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

Chromium infra outage. Should be over? Retrying.

[hbos_chromium, 2016-09-23 13:35:53]

The CQ bit was checked by hbos@chromium.org

[commit-bot: I haz the power, 2016-09-23 13:36:00]

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, 2016-09-23 14:20:08]

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

[commit-bot: I haz the power, 2016-09-23 14:20:10]

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

[hbos_chromium, 2016-09-23 15:09:47]

(No need to take a look, pfeldman, I have the LGTMs, just waiting for the infra
problems to be resolved.)

[hbos_chromium, 2016-09-23 23:01:39]

The CQ bit was checked by hbos@chromium.org

[commit-bot: I haz the power, 2016-09-23 23:02:36]

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, 2016-09-24 01:19:59]

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

[commit-bot: I haz the power, 2016-09-24 01:20:01]

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

[hbos_chromium, 2016-09-24 06:39:31]

The CQ bit was checked by hbos@chromium.org

[commit-bot: I haz the power, 2016-09-24 06:39:40]

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, 2016-09-24 08:38:39]

Description was changed from

==========
WebRTCPeerConnectionHandler::getStats for the new stats collector API.

Adds a new getStats, implemented by RTCPeerConnectionHandler. This is a
part of surfacing the new stats collection API from WebRTC to Blink. In
follow-up CLs the blink::RTCPeerConnection will begin to use it. The old
stats collection API will be kept until the new API has matured.

Main changes:
- MockWebRTCPeerConnectionHandler interface gets a new getStats.
  RTCPeerConnectionHandler implements it, calling the
  webrtc::PeerConnectionInterface's getStats. This involves jumping from
  main thread to signaling thread and back to main thread in a callback.
  The resulting webrtc::RTCStatsReport is surfaced to Blink using a
  content::RTCStatsReport.
- The callback to Blink is performed using the new interface
  blink::WebRTCStatsReportCallback.
- WebRTCStatsMember gets an isDefined function, implemented by
  content::RTCStatsMember.

Test changes:
- MockPeerConnectionImpl implements webrtc::PeerConnectionInterface's
  getStats to return a specified webrtc::RTCStatsReport.
- rtc_peer_connection_handler_test.cc tests RTCPeerConnectionHandler's
  getStats. The test confirms that we get the expected Blink layer stats
  by mocking the WebRTC peer connection to return a stats object defined
  in the test.

BUG=chromium:627816
==========

to

==========
WebRTCPeerConnectionHandler::getStats for the new stats collector API.

Adds a new getStats, implemented by RTCPeerConnectionHandler. This is a
part of surfacing the new stats collection API from WebRTC to Blink. In
follow-up CLs the blink::RTCPeerConnection will begin to use it. The old
stats collection API will be kept until the new API has matured.

Main changes:
- MockWebRTCPeerConnectionHandler interface gets a new getStats.
  RTCPeerConnectionHandler implements it, calling the
  webrtc::PeerConnectionInterface's getStats. This involves jumping from
  main thread to signaling thread and back to main thread in a callback.
  The resulting webrtc::RTCStatsReport is surfaced to Blink using a
  content::RTCStatsReport.
- The callback to Blink is performed using the new interface
  blink::WebRTCStatsReportCallback.
- WebRTCStatsMember gets an isDefined function, implemented by
  content::RTCStatsMember.

Test changes:
- MockPeerConnectionImpl implements webrtc::PeerConnectionInterface's
  getStats to return a specified webrtc::RTCStatsReport.
- rtc_peer_connection_handler_test.cc tests RTCPeerConnectionHandler's
  getStats. The test confirms that we get the expected Blink layer stats
  by mocking the WebRTC peer connection to return a stats object defined
  in the test.

BUG=chromium:627816
==========

[commit-bot: I haz the power, 2016-09-24 08:38:41]

Committed patchset #4 (id:200001)

[commit-bot: I haz the power, 2016-09-24 08:40:34]

Description was changed from

==========
WebRTCPeerConnectionHandler::getStats for the new stats collector API.

Adds a new getStats, implemented by RTCPeerConnectionHandler. This is a
part of surfacing the new stats collection API from WebRTC to Blink. In
follow-up CLs the blink::RTCPeerConnection will begin to use it. The old
stats collection API will be kept until the new API has matured.

Main changes:
- MockWebRTCPeerConnectionHandler interface gets a new getStats.
  RTCPeerConnectionHandler implements it, calling the
  webrtc::PeerConnectionInterface's getStats. This involves jumping from
  main thread to signaling thread and back to main thread in a callback.
  The resulting webrtc::RTCStatsReport is surfaced to Blink using a
  content::RTCStatsReport.
- The callback to Blink is performed using the new interface
  blink::WebRTCStatsReportCallback.
- WebRTCStatsMember gets an isDefined function, implemented by
  content::RTCStatsMember.

Test changes:
- MockPeerConnectionImpl implements webrtc::PeerConnectionInterface's
  getStats to return a specified webrtc::RTCStatsReport.
- rtc_peer_connection_handler_test.cc tests RTCPeerConnectionHandler's
  getStats. The test confirms that we get the expected Blink layer stats
  by mocking the WebRTC peer connection to return a stats object defined
  in the test.

BUG=chromium:627816
==========

to

==========
WebRTCPeerConnectionHandler::getStats for the new stats collector API.

Adds a new getStats, implemented by RTCPeerConnectionHandler. This is a
part of surfacing the new stats collection API from WebRTC to Blink. In
follow-up CLs the blink::RTCPeerConnection will begin to use it. The old
stats collection API will be kept until the new API has matured.

Main changes:
- MockWebRTCPeerConnectionHandler interface gets a new getStats.
  RTCPeerConnectionHandler implements it, calling the
  webrtc::PeerConnectionInterface's getStats. This involves jumping from
  main thread to signaling thread and back to main thread in a callback.
  The resulting webrtc::RTCStatsReport is surfaced to Blink using a
  content::RTCStatsReport.
- The callback to Blink is performed using the new interface
  blink::WebRTCStatsReportCallback.
- WebRTCStatsMember gets an isDefined function, implemented by
  content::RTCStatsMember.

Test changes:
- MockPeerConnectionImpl implements webrtc::PeerConnectionInterface's
  getStats to return a specified webrtc::RTCStatsReport.
- rtc_peer_connection_handler_test.cc tests RTCPeerConnectionHandler's
  getStats. The test confirms that we get the expected Blink layer stats
  by mocking the WebRTC peer connection to return a stats object defined
  in the test.

BUG=chromium:627816

Committed: https://crrev.com/9f64bf32920b4dd5e0eecd59f45b46208a002fd1
Cr-Commit-Position: refs/heads/master@{#420837}
==========

[commit-bot: I haz the power, 2016-09-24 08:40:36]

Patchset 4 (id:??) landed as
https://crrev.com/9f64bf32920b4dd5e0eecd59f45b46208a002fd1
Cr-Commit-Position: refs/heads/master@{#420837}