MojoVideoDecoder: Plumb metadata methods.

media/mojo/interfaces/video_decoder.mojom

Index: media/mojo/interfaces/video_decoder.mojom
diff --git a/media/mojo/interfaces/video_decoder.mojom b/media/mojo/interfaces/video_decoder.mojom
index f0f4ae32b5454c2354725d6554552f3faee51364..6c9d3f138508143d0e4bcdfe937fcaa0d11b0892 100644
--- a/media/mojo/interfaces/video_decoder.mojom
+++ b/media/mojo/interfaces/video_decoder.mojom
@@ -23,25 +23,31 @@ interface VideoDecoder {
   //
   // If |low_delay| is true, the decoder must output frames as soon as possible;
   // in particular, it must not wait for another Decode() request, except as
-  // required for frame reordering.
-  Initialize(VideoDecoderConfig config, bool low_delay) => (bool success);
+  // required for frame reordering. Implementations must fail initialization if
+  // they cannot satisfy this requirement.
+  //
+  // On completion, the callback also includes |needs_bitstream_conversion|,
+  // indicating whether decode buffers need bitstream conversion, and
+  // |max_decode_requests|, the maximum number of concurrent Decode() requests
+  // the implementation supports.
+  Initialize(VideoDecoderConfig config, bool low_delay) =>
+      (bool success, bool needs_bitstream_conversion,
+       int32 max_decode_requests);
 
   // Request decoding of exactly one frame or an EOS buffer. This must not be
-  // called while there are pending Configure(), Reset(), or Decode() requests.
+  // called while there are pending Initialize(), Reset(), or Decode(EOS)
+  // requests.
   //
   // Implementations must eventually execute the callback, even if Decode() is
   // not called again. It is not required that the decode status match the
-  // actual result of decoding a frame; only that decode errors are eventually
-  // reported (such as at EOS). The purpose of the callback is primarily for
-  // Decode() rate control.
-  //
-  // If |buffer| is an EOS buffer, implementations execute all other pending
-  // Decode() callbacks and output all pending frames before executing the EOS
-  // buffer Decode() callback. (That is, they must flush.)
+  // actual result of decoding the buffer, only that decode errors are
+  // eventually reported (such as at EOS).
   //
-  // TODO(sandersd): Plumb GetMaxDecodeRequests() so that parallel Decode()
-  // requests can be allowed.
-  Decode(DecoderBuffer buffer) => (DecodeStatus status);
+  // If |buffer| is an EOS buffer, implementations must execute all other
+  // pending Decode() callbacks and output all pending frames before executing
+  // the Decode(EOS) callback. (That is, they must flush.)
+  Decode(DecoderBuffer buffer) =>
+      (DecodeStatus status, bool can_read_without_stalling);
 
   // Reset the decoder. All ongoing Decode() requests must be completed or
   // aborted before executing the callback. This must not be called while there