Only validate CommandBufferProxyImpl flush if channel exists.

content/common/gpu/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 "content/common/gpu/client/command_buffer_proxy_impl.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/callback.h"
@@ skipping 512 matching lines @@
 
 void CommandBufferProxyImpl::SetLock(base::Lock* lock) {
   lock_ = lock;
 }
 
 bool CommandBufferProxyImpl::IsGpuChannelLost() {
   return !channel_ || channel_->IsLost();
 }
 
 void CommandBufferProxyImpl::EnsureWorkVisible() {
-  channel_->ValidateFlushIDReachedServer(stream_id_, true);
+  if (channel_)
+    channel_->ValidateFlushIDReachedServer(stream_id_, true);
 }
 
 gpu::CommandBufferNamespace CommandBufferProxyImpl::GetNamespaceID() const {
   return gpu::CommandBufferNamespace::GPU_IO;
 }
 
 uint64_t CommandBufferProxyImpl::GetCommandBufferID() const {
   return command_buffer_id_;
 }
 
@@ skipping 266 matching lines @@
 }
 
 void CommandBufferProxyImpl::InvalidGpuReplyOnClientThread() {
   scoped_ptr<base::AutoLock> lock;
   if (lock_)
     lock.reset(new base::AutoLock(*lock_));
   OnDestroyed(gpu::error::kInvalidGpuMessage, gpu::error::kLostContext);
 }
 
 }  // namespace content