Add dedicated PipelineStatus UMAs for encrypted playback

media/filters/decrypting_video_decoder.h

Index: media/filters/decrypting_video_decoder.h
diff --git a/media/filters/decrypting_video_decoder.h b/media/filters/decrypting_video_decoder.h
index 1911c79ab0b6bbcc447085709c631546479fe18c..9b5703878e73900fc6326975329ba02ca0588c5f 100644
--- a/media/filters/decrypting_video_decoder.h
+++ b/media/filters/decrypting_video_decoder.h
@@ -41,6 +41,8 @@ class MEDIA_EXPORT DecryptingVideoDecoder : public VideoDecoder {
               const DecodeCB& decode_cb) override;
   void Reset(const base::Closure& closure) override;
 
+  static const char kDecoderName[];
+
  private:
   // For a detailed state diagram please see this link: http://goo.gl/8jAok
   // TODO(xhwang): Add a ASCII state diagram in this file after this class