gpu: Add flag for enabling asynchronous worker context.

gpu/ipc/client/command_buffer_proxy_impl.cc

 // 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.
 
 #include "gpu/ipc/client/command_buffer_proxy_impl.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/callback.h"
@@ skipping 42 matching lines @@
       flush_count_(0),
       last_put_offset_(-1),
       last_barrier_put_offset_(-1),
       next_fence_sync_release_(1),
       flushed_fence_sync_release_(0),
       verified_fence_sync_release_(0),
       next_signal_id_(0),
       weak_this_(AsWeakPtr()),
       callback_thread_(base::ThreadTaskRunnerHandle::Get()) {
   DCHECK(channel_);
-  DCHECK(stream_id);
+  DCHECK_NE(stream_id, GPU_STREAM_INVALID);
 }
 
 CommandBufferProxyImpl::~CommandBufferProxyImpl() {
   FOR_EACH_OBSERVER(DeletionObserver, deletion_observers_, OnWillDeleteImpl());
   if (channel_) {
     channel_->DestroyCommandBuffer(this);
     channel_ = nullptr;
   }
 }
 
@@ skipping 499 matching lines @@
   const uint64_t token_channel =
       sync_token->command_buffer_id().GetUnsafeValue() >> 32;
   const uint64_t channel = command_buffer_id_.GetUnsafeValue() >> 32;
   if (sync_token->namespace_id() != gpu::CommandBufferNamespace::GPU_IO ||
       token_channel != channel) {
     return false;
   }
 
   // If waiting on a different stream, flush pending commands on that stream.
   const int32_t release_stream_id = sync_token->extra_data_field();
-  if (release_stream_id == 0)
+  if (release_stream_id == gpu::GPU_STREAM_INVALID)
     return false;
 
   if (release_stream_id != stream_id_)
     channel_->FlushPendingStream(release_stream_id);
 
   return true;
 }
 
 void CommandBufferProxyImpl::SignalQuery(uint32_t query,
                                          const base::Closure& callback) {
@@ skipping 185 matching lines @@
   // the client for lost context a single time.
   if (!channel_)
     return;
   channel_->DestroyCommandBuffer(this);
   channel_ = nullptr;
   if (gpu_control_client_)
     gpu_control_client_->OnGpuControlLostContext();
 }
 
 }  // namespace gpu