MediaService: Implement GetChannelToken IPC

media/gpu/ipc/common/media_messages.h

 // Copyright 2016 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.
 
 // Multiply-included message file, hence no include guard here, but see below
 // for a much smaller-than-usual include guard section.
 
+#include <stdint.h>
+
+#include "base/unguessable_token.h"
 #include "gpu/config/gpu_info.h"
 #include "gpu/ipc/common/gpu_param_traits_macros.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/param_traits_macros.h"
 #include "media/gpu/ipc/common/media_param_traits.h"
 #include "media/video/jpeg_decode_accelerator.h"
 #include "media/video/video_decode_accelerator.h"
 #include "media/video/video_encode_accelerator.h"
 #include "ui/gfx/ipc/gfx_param_traits.h"
 
@@ skipping 18 matching lines @@
 IPC_STRUCT_BEGIN(AcceleratedVideoEncoderMsg_Encode_Params2)
   IPC_STRUCT_MEMBER(int32_t, frame_id)
   IPC_STRUCT_MEMBER(base::TimeDelta, timestamp)
   IPC_STRUCT_MEMBER(std::vector<gfx::GpuMemoryBufferHandle>,
                     gpu_memory_buffer_handles)
   IPC_STRUCT_MEMBER(gfx::Size, size)
   IPC_STRUCT_MEMBER(bool, force_keyframe)
 IPC_STRUCT_END()
 
 //------------------------------------------------------------------------------
+// Utility Messages
+
+// Sent from Renderer to GPU process to request a token identifying the channel.
+// These tokens can be used to prove ownership of the channel. The intended use
+// case is to share the command buffer with MojoMediaApplication.
+IPC_SYNC_MESSAGE_CONTROL0_1(GpuCommandBufferMsg_GetChannelToken,
+                            base::UnguessableToken /* channel_token */)
+
+//------------------------------------------------------------------------------
 // Accelerated Video Decoder Messages
 // These messages are sent from Renderer process to GPU process.
 
 // Create and initialize a hardware video decoder using the specified route_id.
 // Created decoders should be freed with AcceleratedVideoDecoderMsg_Destroy when
 // no longer needed.
 IPC_SYNC_MESSAGE_ROUTED2_1(GpuCommandBufferMsg_CreateVideoDecoder,
                            media::VideoDecodeAccelerator::Config /* config */,
                            int32_t /* decoder_route_id */,
                            bool /* succeeded */)
@@ skipping 157 matching lines @@
 IPC_MESSAGE_ROUTED0(AcceleratedJpegDecoderMsg_Destroy)
 
 //------------------------------------------------------------------------------
 // Accelerated JPEG Decoder Host Messages
 // These messages are sent from the GPU process to Browser process.
 //
 // Report decode status.
 IPC_MESSAGE_ROUTED2(AcceleratedJpegDecoderHostMsg_DecodeAck,
                     int32_t, /* bitstream_buffer_id */
                     media::JpegDecodeAccelerator::Error /* error */)