Added a unique command buffer ID for command buffers.

content/common/gpu/gpu_messages.h

 // Copyright (c) 2012 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 <string>
 #include <vector>
 
@@ skipping 457 matching lines @@
 //------------------------------------------------------------------------------
 // GPU Channel Messages
 // These are messages from a renderer process to the GPU process.
 
 // Tells the GPU process to create a new command buffer that renders to an
 // offscreen frame buffer.
 IPC_SYNC_MESSAGE_CONTROL3_1(GpuChannelMsg_CreateOffscreenCommandBuffer,
                             gfx::Size, /* size */
                             GPUCreateCommandBufferConfig, /* init_params */
                             int32, /* route_id */
+                            uint64, /* command_buffer_id */

[piman, 2015/09/15 22:51:05]

I don't think this is needed. You have the route id and the channel id on both
sides.

[David Yen, 2015/09/15 23:09:03]

I accidentally committed this before I was done. I think it is better to pass in
the command_buffer_id because we need to be sure this matches the command buffer
on the client side. My previous patch just had (client_id << 32 | route_id) on
both sides but we have no way of testing that they actually match. What do you
think?

[piman, 2015/09/15 23:17:17]

I prefer not overspecifying the message. My concern is a malicious client
sending a command_buffer_id that doesn't match the route_id/channel_id, which
could cause bugs in the service side if it's not resilient to those being
possibly mismatched.

[David Yen, 2015/09/16 00:02:50]

Ok, I've moved it back.

                             bool /* succeeded */)
 
 // The CommandBufferProxy sends this to the GpuCommandBufferStub in its
 // destructor, so that the stub deletes the actual CommandBufferService
 // object that it's hosting.
 IPC_SYNC_MESSAGE_CONTROL1_0(GpuChannelMsg_DestroyCommandBuffer,
                             int32 /* instance_id */)
 
 #if defined(OS_ANDROID)
 //------------------------------------------------------------------------------
@@ skipping 318 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, /* bitstream_buffer_id */
                     media::JpegDecodeAccelerator::Error /* error */)