Add histogram stats for AV sync stream offset:

webrtc/call/call_perf_tests.cc

Index: webrtc/call/call_perf_tests.cc
diff --git a/webrtc/call/call_perf_tests.cc b/webrtc/call/call_perf_tests.cc
index e27b1fefd29195eab828d23c3b8ae03ecb019552..9c22771edfa07a4e4aa27d60897e87b3bf98d90c 100644
--- a/webrtc/call/call_perf_tests.cc
+++ b/webrtc/call/call_perf_tests.cc
@@ -33,6 +33,7 @@
 #include "webrtc/test/fake_encoder.h"
 #include "webrtc/test/frame_generator.h"
 #include "webrtc/test/frame_generator_capturer.h"
+#include "webrtc/test/histogram.h"
 #include "webrtc/test/rtp_rtcp_observer.h"
 #include "webrtc/test/testsupport/fileutils.h"
 #include "webrtc/test/testsupport/perf_test.h"
@@ -238,6 +239,7 @@ void CallPerfTest::TestAudioVideoSync(FecMode fec,
     rtc::scoped_ptr<RtpHeaderParser> parser_;
   };
 
+  test::ClearHistograms();
   VoiceEngine* voice_engine = VoiceEngine::Create();
   VoEBase* voe_base = VoEBase::GetInterface(voice_engine);
   VoECodec* voe_codec = VoECodec::GetInterface(voice_engine);
@@ -381,6 +383,8 @@ void CallPerfTest::TestAudioVideoSync(FecMode fec,
   DestroyCalls();
 
   VoiceEngine::Delete(voice_engine);
+
+  EXPECT_EQ(1, test::NumHistogramSamples("WebRTC.Video.AVSyncOffsetInMs"));

[stefan-webrtc, 2016/03/04 14:32:17]

Can we also check that the sync offset is reasonable? Or simply wire up the sync
offset to GetStats() and use above, that way we will have a rough idea if it's
correct or not.

[åsapersson, 2016/03/09 15:44:35]

Wired up to and tested through GetStats().

[stefan-webrtc, 2016/03/09 15:59:30]

Thanks a lot!

 }
 
 TEST_F(CallPerfTest, PlaysOutAudioAndVideoInSyncWithVideoNtpDrift) {