More tracing for audio rendering

media/audio/audio_output_resampler.cc

Index: media/audio/audio_output_resampler.cc
diff --git a/media/audio/audio_output_resampler.cc b/media/audio/audio_output_resampler.cc
index c643b3e672c24ed086c07bf5d19262d396b66697..54afbe99fde86847835977ddbc4cebd6180c8013 100644
--- a/media/audio/audio_output_resampler.cc
+++ b/media/audio/audio_output_resampler.cc
@@ -72,6 +72,10 @@ class OnMoreDataConverter
   // stream has been stopped.
   bool error_occurred_;
 
+  // Information about input and output buffer sizes to be traced.
+  const int input_buffer_size_;
+  const int output_buffer_size_;
+
   DISALLOW_COPY_AND_ASSIGN(OnMoreDataConverter);
 };
 
@@ -348,7 +352,9 @@ OnMoreDataConverter::OnMoreDataConverter(const AudioParameters& input_params,
       source_callback_(nullptr),
       input_bytes_per_frame_(input_params.GetBytesPerFrame()),
       audio_converter_(input_params, output_params, false),
-      error_occurred_(false) {}
+      error_occurred_(false),
+      input_buffer_size_(input_params.frames_per_buffer()),
+      output_buffer_size_(output_params.frames_per_buffer()) {}
 
 OnMoreDataConverter::~OnMoreDataConverter() {
   // Ensure Stop() has been called so we don't end up with an AudioOutputStream
@@ -376,6 +382,8 @@ void OnMoreDataConverter::Stop() {
 int OnMoreDataConverter::OnMoreData(AudioBus* dest,
                                     uint32_t total_bytes_delay,
                                     uint32_t frames_skipped) {
+  TRACE_EVENT2("audio", "OnMoreDataConverter::OnMoreData", "input buffer size",

[o1ka, 2016/08/19 13:20:47]

Passing buffer sizes on each trace does not look cute, but it seems to be the
easiest and guaranteed way to get the data. Another way would be to add it to
the native log, but it requires passing log callback all the way from content.
(I'll try to come up with some more or less neat CL for that later).
Note that we can't trace it in the constructor, because at that point tracing is
usually disabled: we will ask a user to enable and record tracing when audio
glitches are observed, i.e. rendering is already ongoing.

[DaleCurtis, 2016/08/19 16:49:00]

Also is it useful to have this information? Isn't it displayed in
chrome://media-internals anyways?

+               input_buffer_size_, "output buffer size", output_buffer_size_);
   current_total_bytes_delay_ = total_bytes_delay;
   audio_converter_.Convert(dest);