Add performance tracing for PlatformThread and parts of the video code.

webrtc/modules/video_coding/frame_buffer2.cc

Index: webrtc/modules/video_coding/frame_buffer2.cc
diff --git a/webrtc/modules/video_coding/frame_buffer2.cc b/webrtc/modules/video_coding/frame_buffer2.cc
index dcbcb1f9bdfd56b1f8cc3c3caa1904d4dfe1dc82..171fc4d6fdf39f0f2a3d3f72b66f030991792bf5 100644
--- a/webrtc/modules/video_coding/frame_buffer2.cc
+++ b/webrtc/modules/video_coding/frame_buffer2.cc
@@ -16,6 +16,7 @@
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
+#include "webrtc/base/trace_event.h"
 #include "webrtc/modules/video_coding/include/video_coding_defines.h"
 #include "webrtc/modules/video_coding/jitter_estimator.h"
 #include "webrtc/modules/video_coding/timing.h"
@@ -55,6 +56,7 @@ FrameBuffer::~FrameBuffer() {}
 FrameBuffer::ReturnReason FrameBuffer::NextFrame(
     int64_t max_wait_time_ms,
     std::unique_ptr<FrameObject>* frame_out) {
+  TRACE_EVENT0("webrtc", "FrameBuffer::NextFrame");

[philipel, 2017/03/03 12:08:34]

If tracing is done in interest of profiling performance then this trace wont
make much sense. Also, not sure if it matters, but this function is recursive
(line 152). :)

[tommi, 2017/03/03 13:07:58]

Both wall clock time and cpu time are useful when profiling.  As is, depending
on the scenario, the thread can spend little or a lot of time sleeping, which is
useful information.  If you use chrome://tracing to look at the data, you'll see
for example that if you have 10 incoming streams, there will be 10 threads, all
of which will be sleeping (on my machine) about 27ms in this function, or close
to 1/10th of a frame, then waking up to decode a frame.

For the purposes of this entry, it doesn't matter if it's recursive, but it will
show up in the trace data when we hit that code path, which can be useful.

   int64_t latest_return_time_ms =
       clock_->TimeInMilliseconds() + max_wait_time_ms;
   int64_t wait_ms = max_wait_time_ms;
@@ -154,22 +156,26 @@ FrameBuffer::ReturnReason FrameBuffer::NextFrame(
 }
 
 void FrameBuffer::SetProtectionMode(VCMVideoProtection mode) {
+  TRACE_EVENT0("webrtc", "FrameBuffer::SetProtectionMode");
   rtc::CritScope lock(&crit_);
   protection_mode_ = mode;
 }
 
 void FrameBuffer::Start() {
+  TRACE_EVENT0("webrtc", "FrameBuffer::Start");
   rtc::CritScope lock(&crit_);
   stopped_ = false;
 }
 
 void FrameBuffer::Stop() {
+  TRACE_EVENT0("webrtc", "FrameBuffer::Stop");
   rtc::CritScope lock(&crit_);
   stopped_ = true;
   new_countinuous_frame_event_.Set();
 }
 
 int FrameBuffer::InsertFrame(std::unique_ptr<FrameObject> frame) {
+  TRACE_EVENT0("webrtc", "FrameBuffer::InsertFrame");
   rtc::CritScope lock(&crit_);
   RTC_DCHECK(frame);
 
@@ -252,6 +258,7 @@ int FrameBuffer::InsertFrame(std::unique_ptr<FrameObject> frame) {
 }
 
 void FrameBuffer::PropagateContinuity(FrameMap::iterator start) {
+  TRACE_EVENT0("webrtc", "FrameBuffer::PropagateContinuity");
   RTC_DCHECK(start->second.continuous);
   if (last_continuous_frame_it_ == frames_.end())
     last_continuous_frame_it_ = start;
@@ -282,6 +289,7 @@ void FrameBuffer::PropagateContinuity(FrameMap::iterator start) {
 }
 
 void FrameBuffer::PropagateDecodability(const FrameInfo& info) {
+  TRACE_EVENT0("webrtc", "FrameBuffer::PropagateDecodability");
   for (size_t d = 0; d < info.num_dependent_frames; ++d) {
     auto ref_info = frames_.find(info.dependent_frames[d]);
     RTC_DCHECK(ref_info != frames_.end());
@@ -291,6 +299,7 @@ void FrameBuffer::PropagateDecodability(const FrameInfo& info) {
 }
 
 void FrameBuffer::AdvanceLastDecodedFrame(FrameMap::iterator decoded) {
+  TRACE_EVENT0("webrtc", "FrameBuffer::AdvanceLastDecodedFrame");
   if (last_decoded_frame_it_ == frames_.end()) {
     last_decoded_frame_it_ = frames_.begin();
   } else {
@@ -316,6 +325,7 @@ void FrameBuffer::AdvanceLastDecodedFrame(FrameMap::iterator decoded) {
 
 bool FrameBuffer::UpdateFrameInfoWithIncomingFrame(const FrameObject& frame,
                                                    FrameMap::iterator info) {
+  TRACE_EVENT0("webrtc", "FrameBuffer::UpdateFrameInfoWithIncomingFrame");
   FrameKey key(frame.picture_id, frame.spatial_layer);
   info->second.num_missing_continuous = frame.num_references;
   info->second.num_missing_decodable = frame.num_references;
@@ -388,6 +398,7 @@ bool FrameBuffer::UpdateFrameInfoWithIncomingFrame(const FrameObject& frame,
 }
 
 void FrameBuffer::UpdateJitterDelay() {
+  TRACE_EVENT0("webrtc", "FrameBuffer::UpdateJitterDelay");
   if (!stats_callback_)
     return;
 
@@ -408,6 +419,7 @@ void FrameBuffer::UpdateJitterDelay() {
 }
 
 void FrameBuffer::ClearFramesAndHistory() {
+  TRACE_EVENT0("webrtc", "FrameBuffer::UpdateJitterDelay");
   frames_.clear();
   last_decoded_frame_it_ = frames_.end();
   last_continuous_frame_it_ = frames_.end();