Add a histogram for video decoder fallback.

media/filters/decoder_stream.cc

Index: media/filters/decoder_stream.cc
diff --git a/media/filters/decoder_stream.cc b/media/filters/decoder_stream.cc
index a67337f757a9d98c4759963f9c186c27a0987ae9..e7313078c287eb064f3f51129dd47be08d0fa590 100644
--- a/media/filters/decoder_stream.cc
+++ b/media/filters/decoder_stream.cc
@@ -9,6 +9,7 @@
 #include "base/debug/trace_event.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "media/base/audio_decoder.h"
 #include "media/base/bind_to_current_loop.h"
@@ -257,11 +258,16 @@ void DecoderStream<StreamType>::OnDecoderSelected(
                                 decoder_->GetDisplayName());
 
   if (state_ == STATE_REINITIALIZING_DECODER) {
+    // Fall back succeeded.
+    if (GetStreamType() == DemuxerStream::VIDEO)

[DaleCurtis, 2015/01/13 19:20:50]

Why the get StreamType() method? Does StreamType == not work?

+      UMA_HISTOGRAM_BOOLEAN("Media.VideoDecoderFallback", true);
     CompleteDecoderReinitialization(true);
     return;
   }
 
   // Initialization succeeded.
+  if (GetStreamType() == DemuxerStream::VIDEO)
+    UMA_HISTOGRAM_BOOLEAN("Media.VideoDecoderFallback", false);
   state_ = STATE_NORMAL;
   if (StreamTraits::NeedsBitstreamConversion(decoder_.get()))
     stream_->EnableBitstreamConverter();