Add UMA metrics for VideoCodec.MP4 and VideoCodec.WebM

media/filters/ffmpeg_glue.h

Index: media/filters/ffmpeg_glue.h
diff --git a/media/filters/ffmpeg_glue.h b/media/filters/ffmpeg_glue.h
index 7d464eb37a67dce62a2c648f0b11046504ac8150..ba245cec2e429db4189832b4ce251c3a13016407 100644
--- a/media/filters/ffmpeg_glue.h
+++ b/media/filters/ffmpeg_glue.h
@@ -30,6 +30,7 @@
 #include <memory>
 
 #include "base/macros.h"
+#include "media/base/container_names.h"
 #include "media/base/media_export.h"
 #include "media/ffmpeg/ffmpeg_deleters.h"
 
@@ -71,11 +72,16 @@ class MEDIA_EXPORT FFmpegGlue {
   // through the FFmpegURLProtocol provided during construction.
   bool OpenContext();
   AVFormatContext* format_context() { return format_context_; }
+  // Returns the container name. Note that it is only available after
+  // calling OpenContext.
+  container_names::MediaContainerName container() const { return container_; }
 
  private:
-  bool open_called_;
-  AVFormatContext* format_context_;
+  bool open_called_ = false;
+  AVFormatContext* format_context_ = nullptr;
   std::unique_ptr<AVIOContext, ScopedPtrAVFree> avio_context_;
+  container_names::MediaContainerName container_ =
+      container_names::CONTAINER_UNKNOWN;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegGlue);
 };