Switch from a DataPipe per DecoderBuffer to a single one.

media/mojo/interfaces/demuxer_stream.mojom

Index: media/mojo/interfaces/demuxer_stream.mojom
diff --git a/media/mojo/interfaces/demuxer_stream.mojom b/media/mojo/interfaces/demuxer_stream.mojom
index 3024942ff29eb288feab44f28ba81924c3d49fa0..4d8885eb52e917eaf8209783ac60afbf93e1ee63 100644
--- a/media/mojo/interfaces/demuxer_stream.mojom
+++ b/media/mojo/interfaces/demuxer_stream.mojom
@@ -30,21 +30,21 @@ interface DemuxerStream {
   // When available, the callback will be invoked with a Status and |response|
   // buffer.  See media::DemuxerStream::ReadCB for explanation of fields.
   //
-  // TODO(tim): Remove this method in favor of initializing the
-  // DemuxerStreamClient with a DataPipeConsumerHandle once we have a framed
-  // DataPipe that we can serialize [|status| | response|]* over directly.
+  // Upon receipt of the callback, clients must fill out the data section of
+  // the returned media::DecoderBuffer by reading from the |pipe| provided
+  // during OnStreamReady().
+  //
+  // TODO(dalecurtis): Remove this method in favor of serializing everything
+  // into the DataPipe given to OnStreamReady() once DataPipe supports framed
+  // data in a nicer fashion.
   Read() => (Status status, MediaDecoderBuffer response);
 };
 
 interface DemuxerStreamClient {
-  // Informs the client that the stream is ready for reading.  If |pipe| is
-  // present, it means the client should read
-  //
-  //     [ |DemuxerStream::Status| |MediaDecoderBuffer| ]
-  //
-  // payloads from the DataPipe directly.  If |pipe| is NULL, it means the
-  // client needs to use DemuxerStream::Read() directly to obtain buffers.
-  OnStreamReady(handle<data_pipe_consumer>? pipe);
+  // Informs the client that the stream is ready for reading.  The client may
+  // then use DemuxerStream::Read() to request buffers.  |pipe| will be used to
+  // fill out the media::DecoderBuffer returned via DemuxerStream::Read().
+  OnStreamReady(handle<data_pipe_consumer> pipe);
 
   // A new AudioDecoderConfig is available. Will be sent by the DemuxerStream
   // whenever a DemuxerStream::STATUS_CONFIG_CHANGED is observed (either