Add video decoding methods in Decryptor and add DecryptingVideoDecoder.

webkit/media/filter_helpers.cc

Index: webkit/media/filter_helpers.cc
diff --git a/webkit/media/filter_helpers.cc b/webkit/media/filter_helpers.cc
index 791aea76b5d534c8fcc9667a28b79c28c0df47ff..d49f7769cf0cbbe6f3ae7efd17a077802a5e16e2 100644
--- a/webkit/media/filter_helpers.cc
+++ b/webkit/media/filter_helpers.cc
@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "media/base/filter_collection.h"
 #include "media/base/message_loop_factory.h"
+#include "media/filters/decrypting_video_decoder.h"
 #include "media/filters/chunk_demuxer.h"
 #include "media/filters/dummy_demuxer.h"
 #include "media/filters/ffmpeg_audio_decoder.h"
@@ -18,6 +19,12 @@
 namespace webkit_media {
 
 // Constructs and adds the default audio/video decoders to |filter_collection|.
+// Note that decoders in the |filter_collection| are ordered. The first
+// audio/video decoder in the |filter_collection| that supports the input
+// audio/video stream will be selected as the audio/video decoder in the media
+// pipeline. This is done by trying to initialize the decoder with the input
+// stream. Some decoder may only accept certain types of streams. For example,
+// DecryptingVideoDecoder only supports encrypted video stream.
 static void AddDefaultDecodersToCollection(
     media::MessageLoopFactory* message_loop_factory,
     media::FilterCollection* filter_collection,
@@ -27,12 +34,21 @@ static void AddDefaultDecodersToCollection(
                  base::Unretained(message_loop_factory),
                  media::MessageLoopFactory::kDecoder)));
 
+  scoped_refptr<media::DecryptingVideoDecoder> decrypting_video_decoder =
+      new media::DecryptingVideoDecoder(
+          base::Bind(&media::MessageLoopFactory::GetMessageLoop,
+                     base::Unretained(message_loop_factory),
+                     media::MessageLoopFactory::kDecoder),
+          decryptor);
+
   scoped_refptr<media::FFmpegVideoDecoder> ffmpeg_video_decoder =
       new media::FFmpegVideoDecoder(
           base::Bind(&media::MessageLoopFactory::GetMessageLoop,
                      base::Unretained(message_loop_factory),
                      media::MessageLoopFactory::kDecoder),
           decryptor);
+
+  filter_collection->GetVideoDecoders()->push_back(decrypting_video_decoder);
   filter_collection->GetVideoDecoders()->push_back(ffmpeg_video_decoder);
 }