Check that |gpu_channel_host_| is not NULL before passing it along.

content/renderer/render_thread_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/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <vector>
@@ skipping 1409 matching lines @@
 
   scoped_refptr<GpuChannelHost> gpu_channel_host = GetGpuChannel();
   scoped_refptr<media::GpuVideoAcceleratorFactories> gpu_factories;
   scoped_refptr<base::SingleThreadTaskRunner> media_task_runner =
       GetMediaThreadTaskRunner();
   if (!gpu_va_context_provider_.get() ||
       gpu_va_context_provider_->DestroyedOnMainThread()) {
     if (!gpu_channel_host.get()) {
       gpu_channel_host = EstablishGpuChannelSync(
           CAUSE_FOR_GPU_LAUNCH_WEBGRAPHICSCONTEXT3DCOMMANDBUFFERIMPL_INITIALIZE);
     }

[Pawel Osciak, 2015/07/21 00:15:00]

Should we be checking gpu_channel_host again here?

[sandersd (OOO until July 31), 2015/07/21 00:35:01]

Both WebGraphicsContext3DCommandBufferImpl::CreateOffscreenContext() and
ContextProviderCommandBuffer::Create() check for and then return NULL, so at the
very least the result is safe (and matches my expectations about correct
behavior).

     blink::WebGraphicsContext3D::Attributes attributes;
     bool lose_context_when_out_of_memory = false;
     gpu_va_context_provider_ = ContextProviderCommandBuffer::Create(
         make_scoped_ptr(
             WebGraphicsContext3DCommandBufferImpl::CreateOffscreenContext(
                 gpu_channel_host.get(), attributes,
                 lose_context_when_out_of_memory,
                 GURL("chrome://gpu/RenderThreadImpl::GetGpuVDAContext3D"),
                 WebGraphicsContext3DCommandBufferImpl::SharedMemoryLimits(),
                 NULL)),
         GPU_VIDEO_ACCELERATOR_CONTEXT);
   }
   if (gpu_va_context_provider_.get()) {
     bool enable_video_accelerator =
         !cmd_line->HasSwitch(switches::kDisableAcceleratedVideoDecode);
     std::string image_texture_target_string =
         cmd_line->GetSwitchValueASCII(switches::kContentImageTextureTarget);
     unsigned image_texture_target = 0;
     bool parsed_image_texture_target =
         base::StringToUint(image_texture_target_string, &image_texture_target);
     DCHECK(parsed_image_texture_target);
+    CHECK(gpu_channel_host.get());

[jochen (gone - plz use gerrit), 2015/07/21 14:12:58]

please add a comment pointing at the crbug, and consider printing something when
you hit the CHECK(), e.g.

CHECK(gpu_channel_host.get()) << "No gpu_channel_host?? see crbug.com/495185";

[sandersd (OOO until July 31), 2015/07/21 17:29:57]

Done.

     gpu_factories = RendererGpuVideoAcceleratorFactories::Create(
         gpu_channel_host.get(), media_task_runner, gpu_va_context_provider_,
         image_texture_target, enable_video_accelerator);
   }
   return gpu_factories;
 }
 
 scoped_ptr<WebGraphicsContext3DCommandBufferImpl>
 RenderThreadImpl::CreateOffscreenContext3d() {
   blink::WebGraphicsContext3D::Attributes attributes(GetOffscreenAttribs());
@@ skipping 571 matching lines @@
 }
 
 void RenderThreadImpl::PendingRenderFrameConnect::OnConnectionError() {
   size_t erased =
       RenderThreadImpl::current()->pending_render_frame_connects_.erase(
           routing_id_);
   DCHECK_EQ(1u, erased);
 }
 
 }  // namespace content