Commit Graph

96 Commits

Author SHA1 Message Date
58d992e025 Add macros for ability to log samples that are added to histograms (RTC_LOGGED_*).
Adds logging of:
- video stats that are recorded when a stream is removed
- bitrate stats that are recorded at the end of a call
- initial bwe rampup stats

BUG=

Review URL: https://codereview.webrtc.org/1788783002

Cr-Commit-Position: refs/heads/master@{#12133}
2016-03-29 09:15:11 +00:00
7ade7b3282 Delete class webrtc::VideoRenderer and its header file.
To replace the SmoothsRenderedFrames method, added a corresponding
flag to VideoReceiveStream::Config instead.

BUG=webrtc:5426

Review URL: https://codereview.webrtc.org/1818023002

Cr-Commit-Position: refs/heads/master@{#12102}
2016-03-23 11:48:17 +00:00
7a43d253f9 Make the audio channel communicate network state changes to the call.
This change enables voice-only calls to keep track of the network state.
This is only a partial fix - the last modality to change state controls
the state for the entire call, so a call with a failed video transport
will also stop sending audio packets. Handling this condition correctly
would require the call to keep track of network state for each media
type separately, and take care of conditions such as a failed video
channel getting removed, while a functioning audio channel remains.

BUG=webrtc:5307

Review URL: https://codereview.webrtc.org/1757683002

Cr-Commit-Position: refs/heads/master@{#12093}
2016-03-22 22:32:31 +00:00
eb83a1a10f This is an initial cleanup step, aiming to delete the
webrtc::VideoRenderer class, replacing it by rtc::VideoSinkInterface.

The next step is to convert all places where a renderer is attached to
rtc::VideoSourceInterface, and at that point, the
SmoothsRenderedFrames method can be replaced by a flag
rtc::VideoSinkWants::smoothed_frames.

Delete unused method IsTextureSupported.
Delete unused time argument to RenderFrame.
Let webrtc::VideoRenderer inherit rtc::VideoSinkInterface. Rename RenderFrame --> OnFrame.

TBR=kjellander@webrtc.org
BUG=webrtc:5426

Review URL: https://codereview.webrtc.org/1814763002

Cr-Commit-Position: refs/heads/master@{#12070}
2016-03-21 08:28:06 +00:00
94a23f04af Reland "Add check_deps rules in DEPS files."
Relanding https://codereview.webrtc.org/1796413002/
without the change to the openmax_dl include path
(which broke downstream code).

TBR=tommi@webrtc.org
BUG=webrtc:5623
TESTED=Passing runs using:
buildtools/checkdeps/checkdeps.py --root=. talk
buildtools/checkdeps/checkdeps.py --root=. webrtc

Review URL: https://codereview.webrtc.org/1804333002 .

Cr-Commit-Position: refs/heads/master@{#12031}
2016-03-17 11:05:50 +00:00
56cf60e717 Revert of Add check_deps rules in DEPS files. (patchset #2 id:60001 of https://codereview.webrtc.org/1796413002/ )
Reason for revert:
The openmax_dl include change breaks downstream projects.

Original issue's description:
> Add check_deps rules in DEPS files.
>
> Add fine-grained check_deps rules for all of WebRTC.
> This will help both maintaining sane dependencies and provides a way
> to visualize dependency graphs using the buildtools/checkdeps/graphdeps.py script.
>
> Example:
> buildtools/checkdeps/graphdeps.py --root=. --format=png \
> --out=./webrtc.png --incl='^webrtc/modules/bitrate_controller->' \
> --excl='chromium|base|external|testing|webrtc/test|\.h$|\.cc$'
>
> will produce a neat webrtc.png image showcasing the dependencies
> (according to the DEPS file) for the bitrate_controller module.
> Some dependencies are filtered out for readability.
>
> BUG=webrtc:5623
> TESTED=Passing runs using:
> buildtools/checkdeps/checkdeps.py --root=. talk
> buildtools/checkdeps/checkdeps.py --root=. webrtc
>
> R=tommi@webrtc.org
>
> Committed: https://crrev.com/086f851b7b9b4bcbd4fe507c3bf83b760bd7f4d9
> Cr-Commit-Position: refs/heads/master@{#12008}

TBR=tommi@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:5623

Review URL: https://codereview.webrtc.org/1808573002

Cr-Commit-Position: refs/heads/master@{#12009}
2016-03-16 00:41:04 +00:00
086f851b7b Add check_deps rules in DEPS files.
Add fine-grained check_deps rules for all of WebRTC.
This will help both maintaining sane dependencies and provides a way
to visualize dependency graphs using the buildtools/checkdeps/graphdeps.py script.

Example:
buildtools/checkdeps/graphdeps.py --root=. --format=png \
--out=./webrtc.png --incl='^webrtc/modules/bitrate_controller->' \
--excl='chromium|base|external|testing|webrtc/test|\.h$|\.cc$'

will produce a neat webrtc.png image showcasing the dependencies
(according to the DEPS file) for the bitrate_controller module.
Some dependencies are filtered out for readability.

BUG=webrtc:5623
TESTED=Passing runs using:
buildtools/checkdeps/checkdeps.py --root=. talk
buildtools/checkdeps/checkdeps.py --root=. webrtc

R=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1796413002 .

Cr-Commit-Position: refs/heads/master@{#12008}
2016-03-16 00:22:53 +00:00
6021fe2b1e Clean away use of RtpAudioFeedback interface from RTP/RTCP sender code.
BUG=webrtc:4690

Review URL: https://codereview.webrtc.org/1803923003

Cr-Commit-Position: refs/heads/master@{#12003}
2016-03-15 18:41:58 +00:00
f8cdd184d5 Add histogram stats for AV sync stream offset:
"WebRTC.Video.AVSyncOffsetInMs"

The absolute value of the sync offset between a rendered video frame and the latest played audio frame is measured per video frame. The average offset per received video stream is recorded when a stream is removed.

Updated sync tests in call_perf_tests.cc to use this implementation.

BUG=webrtc:5493

Review URL: https://codereview.webrtc.org/1756193005

Cr-Commit-Position: refs/heads/master@{#11993}
2016-03-15 08:00:54 +00:00
b25345ee3f Replace scoped_ptr with unique_ptr in webrtc/call/
BUG=webrtc:5520

Review URL: https://codereview.webrtc.org/1789903003

Cr-Commit-Position: refs/heads/master@{#11970}
2016-03-12 14:10:53 +00:00
86aabb288d Move BitrateAllocator reference from ViEEncoder to VideoSendStream.
This CL will be followed up with a CL adding AudioSendStream to
BitrateAllocator, so this is a small CL to have the video connection to
BitrateAllocator "at the same level" as for audio.

BUG=webrtc:5079
R=stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1785283002 .

Cr-Commit-Position: refs/heads/master@{#11955}
2016-03-11 14:44:44 +00:00
905f8e7e9d Make ReconfigureVideoEncoder void.
Also moves and simplifies SetSendCodec from VideoSendStream to mostly
inside ViEEncoder. This is necessary for making
ReconfigureVideoEncoder asynchronous as we don't post any result back.

BUG=webrtc:5494
R=stefan@webrtc.org
TBR=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1754283002 .

Cr-Commit-Position: refs/heads/master@{#11847}
2016-03-02 16:00:07 +00:00
ac287ee8b5 VideoCaptureInput enforce VideoFrame::render_time to be generated by webrtc clock.
render_time time field (means capture time for sender side) is used by rtcp SenderReport to calculate offset since last frame and to estimate rtp timestamp for the time SenderReport should be send at.
mapping between rtp timestamp and ntp time in SenderReport is used for stream synchronization.

calculation of rtp_timestamp (using ntp_time of incoming video frame) for rtp packets is unchanged.

BUG=webrtc:5433, webrtc:5504, webrtc:5505

Review URL: https://codereview.webrtc.org/1693443002

Cr-Commit-Position: refs/heads/master@{#11820}
2016-02-29 20:17:10 +00:00
c379fcb248 Break out pacer thread from CongestionController to increase testability.
R=pbos@webrtc.org
TBR=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1732863002 .

Cr-Commit-Position: refs/heads/master@{#11745}
2016-02-24 15:03:08 +00:00
f4d8441aed Disabled flaky tests
BUG=webrtc:5576

TBR=stefan@webrtc.org, pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1729533002 .

Cr-Commit-Position: refs/heads/master@{#11722}
2016-02-23 17:56:49 +00:00
80e12072cf Move congestion controller to a separate module.
This allows other projects to more easily depend on this.

The plan is to move remote_bitrate_estimator and bitrate_controller into this module and reduce the exposed interface to only a simplified version of congestion_controller.h.

No functional changes in this CL.

R=mflodman@webrtc.org, pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1718473002 .

Cr-Commit-Position: refs/heads/master@{#11718}
2016-02-23 12:30:51 +00:00
e2d83d6560 Use CallStats for RTT in Call, rather than VideoSendStream::GetRtt()
Also move some stats reporting from vie_channel to send stats proxy

BUG=

Review URL: https://codereview.webrtc.org/1669623004

Cr-Commit-Position: refs/heads/master@{#11688}
2016-02-19 17:03:34 +00:00
789ba92e14 Simplify CongestionController.
- Removes the dependency on CallStats.
- Implements Module interface so that we don't have to register
  each internal component to the process thread separately.

R=pbos@webrtc.org, solenberg@webrtc.org

Review URL: https://codereview.webrtc.org/1704983002 .

Cr-Commit-Position: refs/heads/master@{#11655}
2016-02-17 14:52:25 +00:00
69e59e619a [rtp_rtcp] rtc::scoped_ptr<rtcp::RawPacket> replaced with rtc::Buffer
rtcp::RawPacket is rtc::Buffer, it had no extra functionality.
rtc::Buffer is a movable class - no point to wrap it into rtc::scoped_ptr
change is large, but straightforward:
  rtc::scoped_ptr<rtcp::RawPacket> replaced with rtc::Buffer
  ->Buffer() replaced with .data()
  ->Length() replaced with .size()

BUG=webrtc:5260

Review URL: https://codereview.webrtc.org/1696203002

Cr-Commit-Position: refs/heads/master@{#11649}
2016-02-17 11:11:50 +00:00
62a5ccdb53 Update bitrate only when we have incoming packet.
Also cleans up some unused code and makes sure the min bitrate of the BWE can't be set to anything lower than 10 kbps.

BUG=webrtc:5474
R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1699903003 .

Cr-Commit-Position: refs/heads/master@{#11636}
2016-02-16 16:07:31 +00:00
cde5d6b305 removed five redundant avsync tests to make webrtc_perf_test faster
R=kwiberg@webrtc.org, pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1689163002 .

Cr-Commit-Position: refs/heads/master@{#11620}
2016-02-15 10:15:10 +00:00
8c66a00a37 Initialize VideoSendStream members in constructor.
Removes scoped_ptrs and provides clearer lifetime between objects.

BUG=webrtc:5494
R=stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1674663002 .

Cr-Commit-Position: refs/heads/master@{#11571}
2016-02-11 12:51:18 +00:00
9c6a0c7f6d Added A/V sync tests with drifting clocks.
adding 30% drift to media generator (e.g. audio frame generated every 7ms instead of promised 10ms) works fine
adding 2% drift to video ntp-timestamp-stamper makes A/V sync fail.

BUG=webrtc:5504
R=pbos@webrtc.org,stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1674413004

Cr-Commit-Position: refs/heads/master@{#11556}
2016-02-10 18:54:52 +00:00
58c664c13d Clean up of CongestionController.
Removes unused methods and moves out ViERemb to Call.

R=pbos@webrtc.org, solenberg@webrtc.org

Review URL: https://codereview.webrtc.org/1663413003 .

Cr-Commit-Position: refs/heads/master@{#11527}
2016-02-08 13:31:53 +00:00
ba4c0e45ff Add send-side BWE to WebRtcVoiceEngine under a finch experiment.
This adds negotiation of both transport sequence number and transport
feedback. Only offers transport seq num if the
WebRTC-Audio-SendSideBwe finch experiment is enabled.

TBR=mflodman@webrtc.org
BUG=webrtc:5263

Review URL: https://codereview.webrtc.org/1604563002

Cr-Commit-Position: refs/heads/master@{#11487}
2016-02-04 12:12:31 +00:00
bba9dec4d5 Use separate rtp module lists for send and receive in PacketRouter.
This makes it possible to handle send and receive streams with the same SSRC, which is currently the case in some peer connection tests.

Also moves sending transport feedback to the pacer thread.

BUG=webrtc:5263

Review URL: https://codereview.webrtc.org/1628683002

Cr-Commit-Position: refs/heads/master@{#11443}
2016-02-01 12:40:04 +00:00
28ba92731d Switch to use new implementation in metrics.h.
Sparse macro replaced for all video histograms that have a constant name.

BUG=webrtc:5283

Review URL: https://codereview.webrtc.org/1616153005

Cr-Commit-Position: refs/heads/master@{#11368}
2016-01-25 13:58:27 +00:00
5ad935cb56 Remove mutable from rtc::CriticalSection members.
rtc::CriticalSection is now lockable from const methods and no longer
need to remain mutable.

BUG=
R=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1613643004

Cr-Commit-Position: refs/heads/master@{#11367}
2016-01-25 11:52:53 +00:00
429c345b02 Fixes a bug which incorrectly logs incoming RTCP as outgoing.
Adds logging to RTPSender and RTCPSender, pushing an event log pointer from Channel through ModuleRtpRtcpImpl to the Sender objects.

BUG=webrtc:4741

Review URL: https://codereview.webrtc.org/1571283002

Cr-Commit-Position: refs/heads/master@{#11336}
2016-01-21 13:42:10 +00:00
32f81542c2 Support REMB in combination with send-side BWE.
BUG=webrtc:4173

Review URL: https://codereview.webrtc.org/1581113006

Cr-Commit-Position: refs/heads/master@{#11322}
2016-01-20 15:14:03 +00:00
63cb434691 Switch use of CriticalSectionWrapper -> rtc::CriticalSection in call/
This is a first cl of removing use of CriticalSectionWrapper after a series of cleanup CLs that have been landing recently (and still are landing).

BUG=

Review URL: https://codereview.webrtc.org/1610553002

Cr-Commit-Position: refs/heads/master@{#11316}
2016-01-20 10:32:58 +00:00
7b971e728b Remove extra_options from VideoCodec.
Constructing default options is racy when initializing multiple VP8
encoders in parallel. This is only used for VP8 temporal layers. Adding
TemporalLayerFactory to VP8 codec specifics instead of generic options.

Removes the last webrtc::Config uses/includes from video code.

Also removes VideoCodec equality operators which are no longer in use.

BUG=webrtc:5410
R=stefan@webrtc.org
TBR=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1606613003 .

Cr-Commit-Position: refs/heads/master@{#11307}
2016-01-19 15:26:24 +00:00
34ed2b95a5 [rtp_rtcp] rtcp::SenderReport moved into own file and got Parse function
BUG=webrtc:5260
R=åsapersson

Review URL: https://codereview.webrtc.org/1544983002

Cr-Commit-Position: refs/heads/master@{#11288}
2016-01-18 10:43:38 +00:00
ff2a6351e0 Add ramp-up tests for transport sequence number with and w/o audio.
Also add a perf metric tracking the average network latency.

The audio stream test is disabled for now since audio isn't included in bitrate allocation.

BUG=webrtc:5263
R=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1582833002 .

Cr-Commit-Position: refs/heads/master@{#11244}
2016-01-14 09:00:34 +00:00
ea8c0f6fcb Fix capture ntp time issue introduced with r11187.
I think the problem was that I only introduced delay in one direction, and the estimation assumes that the RTT is evenly divided between the send direction and the receive direction, which was true for the old test.

BUG=chromium:576246
R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1577853005 .

Cr-Commit-Position: refs/heads/master@{#11233}
2016-01-13 07:58:52 +00:00
d20e651327 Fix test bug introduced in r11101.
BUG=chromium:572995
R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1578223002 .

Cr-Commit-Position: refs/heads/master@{#11224}
2016-01-12 14:51:28 +00:00
3842c5c7f7 Wire-up BWE feedback for audio receive streams.
Also wires up receiving transport sequence numbers.

BUG=webrtc:5263
R=mflodman@webrtc.org, pbos@webrtc.org, solenberg@webrtc.org

Review URL: https://codereview.webrtc.org/1535963002 .

Cr-Commit-Position: refs/heads/master@{#11220}
2016-01-12 12:55:11 +00:00
f1685c771d Disable RampUpTest.UpDownUp* in webrtc_perf_tests on Mac
NOTRY=True
BUG=5407
TBR=stefan@webrtc.org,pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1569273003

Cr-Commit-Position: refs/heads/master@{#11188}
2016-01-08 18:43:45 +00:00
e74eef19bd Add CreateSend/ReceiveTransport() methods to CallTest.
This allows the test to create its own transports if it, for instance, needs to do demuxing.

BUG=webrtc:5416

Review URL: https://codereview.webrtc.org/1573453002

Cr-Commit-Position: refs/heads/master@{#11187}
2016-01-08 14:47:21 +00:00
9fea80f50d Add audio streams to CallTest and a first A/V call test.
Add audio send and receive streams to CallTest and call the necessary voice engine APIs for the streams to be usable. Verifies the implementation by adding a simple test which monitors outgoing packets and checks that both audio and video is being sent with transport sequence numbers.

Audio streams are using a fake audio device with file input.

The CallTest implementation is to a big degree based on call_perf_tests.cc and should in the future replace a lot of that code.

R=pbos@webrtc.org
TBR=kjellander@webrtc.org

BUG=webrtc:5263

Review URL: https://codereview.webrtc.org/1542653002 .

Cr-Commit-Position: refs/heads/master@{#11171}
2016-01-07 16:43:31 +00:00
e2976c87f7 Remove DISABLED_ON_ macros.
Macro incorrectly displays DISABLED_ON_ANDROID in test names for
parameterized tests under --gtest_list_tests, causing tests to be
disabled on all platforms since they contain the DISABLED_ prefix rather
than their expanded variants.

This expands the macro variants to inline if they're disabled or not,
and removes building some tests under configurations where they should
fail, instead of building them but disabling them by default.

The change also removes gtest_disable.h as an unused include from many
other files.

BUG=webrtc:5387, webrtc:5400
R=kjellander@webrtc.org, phoglund@webrtc.org
TBR=henrik.lundin@webrtc.org

Review URL: https://codereview.webrtc.org/1547343002 .

Cr-Commit-Position: refs/heads/master@{#11150}
2016-01-04 21:44:16 +00:00
ff483617a4 Step 1 to prepare call_test.* for combined audio/video tests.
Also move (and clean up includes) rampup_tests.* to webrtc/call in preparation for combined audio/video ramp-up tests.

No functional changes.

BUG=webrtc:5263

Review URL: https://codereview.webrtc.org/1537273003

Cr-Commit-Position: refs/heads/master@{#11101}
2015-12-21 11:14:05 +00:00
53805324c0 Rename RTC_HISTOGRAM_* macros to RTC_HISTOGRAM_*_SPARSE_* to indicate that these are for infrequent updates.
This implementation will be replaced by a faster one and sparse will be removed.

BUG=webrtc:5283

Review URL: https://codereview.webrtc.org/1530913002

Cr-Commit-Position: refs/heads/master@{#11099}
2015-12-21 09:46:25 +00:00
5811a39f14 Replace EventWrapper in video/, test/ and call/.
Makes use of rtc::Event which is simpler and can be used without
allocating additional objects on the heap.

Does not modify test/channel_transport/.

BUG=
R=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1487893004 .

Cr-Commit-Position: refs/heads/master@{#10968}
2015-12-10 12:03:00 +00:00
84e78f9102 Rewrote the PRNG using an xorshift* algorithm and moved the files from test/ to base/.
Created a simple unit test for the new random number generator. (It mostly tests
that the generated numbers are consistent with the intended distribution, e.g. uniform.
It is not a comprehensive test of the quality of the random numbers.)

Several assertions in OveruseDetectorTest seem to depend on the exact sequence of random numbers. I updated those numbers to work with the new PRNG.

Compute the standard deviation of the expected result in TestReorderFilter instead of passing an uncertainty parameter.

BUG=webrtc:5177

Review URL: https://codereview.webrtc.org/1457023002

Cr-Commit-Position: refs/heads/master@{#10965}
2015-12-10 09:51:02 +00:00
7623ce4aeb Reland of Merge webrtc/video_engine/ into webrtc/video/ (patchset #2 id:300001 of https://codereview.webrtc.org/1507903005/ )
Reason for revert:
Bot breakage caused by TickTime::UseFakeClock has been removed.

Original issue's description:
> Revert of Merge webrtc/video_engine/ into webrtc/video/ (patchset #2 id:20001 of https://codereview.webrtc.org/1506773002/ )
>
> Reason for revert:
> Breaks Dr Memory Light https://build.chromium.org/p/client.webrtc/builders/Win%20DrMemory%20Light/builds/4643 and all the Android Tests bots.
>
> Original issue's description:
> > Merge webrtc/video_engine/ into webrtc/video/
> >
> > BUG=webrtc:1695
> > R=mflodman@webrtc.org
> >
> > Committed: https://crrev.com/03ef053202bc5d5ab43460eebf5403232f157646
> > Cr-Commit-Position: refs/heads/master@{#10926}
>
> TBR=mflodman@webrtc.org,pbos@webrtc.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=webrtc:1695
>
> Committed: https://crrev.com/8237abf563bf4782ee104408b53cc8e55ce44518
> Cr-Commit-Position: refs/heads/master@{#10937}

BUG=webrtc:1695
TBR=mflodman@webrtc.org,kjellander@webrtc.org
NOPRESUBMIT=true

Review URL: https://codereview.webrtc.org/1510183002 .

Cr-Commit-Position: refs/heads/master@{#10948}
2015-12-09 11:13:40 +00:00
d3c944755e Nuke TickTime::UseFakeClock.
Removes the global simulated time that affects (or breaks) following
tests in the same binary and replaces it with SimulatedClock.

BUG=webrtc:5318
R=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1512853002 .

Cr-Commit-Position: refs/heads/master@{#10947}
2015-12-09 10:21:09 +00:00
8237abf563 Revert of Merge webrtc/video_engine/ into webrtc/video/ (patchset #2 id:20001 of https://codereview.webrtc.org/1506773002/ )
Reason for revert:
Breaks Dr Memory Light https://build.chromium.org/p/client.webrtc/builders/Win%20DrMemory%20Light/builds/4643 and all the Android Tests bots.

Original issue's description:
> Merge webrtc/video_engine/ into webrtc/video/
>
> BUG=webrtc:1695
> R=mflodman@webrtc.org
>
> Committed: https://crrev.com/03ef053202bc5d5ab43460eebf5403232f157646
> Cr-Commit-Position: refs/heads/master@{#10926}

TBR=mflodman@webrtc.org,pbos@webrtc.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:1695

Review URL: https://codereview.webrtc.org/1507903005

Cr-Commit-Position: refs/heads/master@{#10937}
2015-12-08 15:12:11 +00:00
03ef053202 Merge webrtc/video_engine/ into webrtc/video/
BUG=webrtc:1695
R=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1506773002 .

Cr-Commit-Position: refs/heads/master@{#10926}
2015-12-08 08:09:07 +00:00
6f28cf0b95 Implement standalone event tracing in AppRTCDemo.
Logs tracing events (TRACE_EVENT0 and friends) to storage in a format
compatible with chrome://tracing which can be used for performance
evaluation, finding lock contention and other sweet things). Tracing is
still basic and doesn't contain thread metadata or logging of tracing
arguments.

BUG=webrtc:5158
R=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1457383002 .

Cr-Commit-Position: refs/heads/master@{#10921}
2015-12-07 22:17:26 +00:00