Add Mojo interfaces for GpuJpegDecodeAccelerator and GpuJpegDecodeAcceleratorHost

media/gpu/mojo/jpeg_decoder.mojom

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module media.mojom;
+
+import "media/mojo/interfaces/media_types.mojom";
+import "ui/gfx/geometry/mojo/geometry.mojom";
+
+enum Error {
+  NO_ERRORS,
+  INVALID_ARGUMENT,
+  UNREADABLE_INPUT,
+  PARSE_JPEG_FAILED,
+  UNSUPPORTED_JPEG,
+  PLATFORM_FAILURE,
+};
+
+struct JpegDecodeInfo {
+  BitstreamBuffer input_buffer;
+  gfx.mojom.Size coded_size;
+  handle<shared_buffer> output_handle;
+  uint32 output_buffer_size;
+};
+
+interface GpuJpegDecodeAcceleratorClient {
+  // Report decode status.
+  OnDecodeAck(int32 bitstream_buffer_id, Error error);
+};
+
+interface GpuJpegDecodeAccelerator {
+  // Create and initialize a hardware jpeg decoder.
+  // Created decoder should be freed with Uninitialize() when no longer needed.
+  Initialize(GpuJpegDecodeAcceleratorClient client) => (bool success);

[chfremer, 2017/05/30 18:07:24]

nit: Comment is slightly confusing. If we say "Creates a hardware decoder" it
sounds like we can create more than one and use them simultaneously. But since
Uninitialize() does not take any parameters, the API really only allows for a
single decoder at a time.

I recommend removing the method-level comments for Initialize() and
Uninitialize() and instead use an interface-level comment to explaing that
Initialize() must be called before using Decode() and Uninitialize() must be
called before releasing the instance (assuming you do not want to drop the
method altogether and do the uninitialization automatically on releasing).

[Chandan, 2017/05/31 13:19:58]

Uninitialize() is most likely to be removed. Hence, I did not add any comment
w.r.t it for now. In case, we keep Uninitialize(), I will update accordingly.

+
+  // Decode one JPEG image from shared memory |input_buffer_handle| with size
+  // |input_buffer_size|. The input buffer is associated with |input_buffer_id|
+  // and the size of JPEG image is |coded_size|. Decoded I420 frame data will
+  // be put onto shared memory associated with |output_video_frame_handle|
+  // with size limit |output_buffer_size|.
+  Decode(JpegDecodeInfo info);
+
+  // TODO(c.padhi): This method might not be required, see
+  // http://crbug.com/699255.
+  // Destroy request to the decoder.
+  Uninitialize();
+};