Added BitsPerChannel method to video frame class.

media/base/video_frame.h

Index: media/base/video_frame.h
diff --git a/media/base/video_frame.h b/media/base/video_frame.h
index 7ed1162b7a4147956f0d01d95c971ce7bbf4a0ab..38bc1a361479d0ce666e7135ddbbefb0d075d0a6 100644
--- a/media/base/video_frame.h
+++ b/media/base/video_frame.h
@@ -393,6 +393,9 @@ class MEDIA_EXPORT VideoFrame : public base::RefCountedThreadSafe<VideoFrame> {
   // guaranteed to be unique within a single process.
   int unique_id() const { return unique_id_; }
 
+  // Returns the number of bits per channel for given |format|.
+  int BitsPerChannel(VideoPixelFormat format);
+
  protected:
   friend class base::RefCountedThreadSafe<VideoFrame>;