[Chromecast] Add metrics for logging platform A/V bitrate estimates.

chromecast/media/cma/pipeline/av_pipeline_impl.h

Index: chromecast/media/cma/pipeline/av_pipeline_impl.h
diff --git a/chromecast/media/cma/pipeline/av_pipeline_impl.h b/chromecast/media/cma/pipeline/av_pipeline_impl.h
index 4dfe09169b599864e80b29a8bd0d32aa4fe1aaa8..ad44026edaac46737ed7d33eb9e5f6e5f2c4702d 100644
--- a/chromecast/media/cma/pipeline/av_pipeline_impl.h
+++ b/chromecast/media/cma/pipeline/av_pipeline_impl.h
@@ -54,6 +54,10 @@ class AvPipelineImpl : MediaPipelineBackend::Decoder::Delegate {
 
   virtual void UpdateStatistics() = 0;
 
+  int bytes_decoded_since_last_update() const {
+    return bytes_decoded_since_last_update_;
+  }
+
  protected:
   // Pipeline states.
   enum State {
@@ -80,6 +84,7 @@ class AvPipelineImpl : MediaPipelineBackend::Decoder::Delegate {
                              size_t max_frame_size);
 
   ::media::PipelineStatistics previous_stats_;
+  int bytes_decoded_since_last_update_;
 
  private:
   void OnFlushDone();