cc: Add null checks for GrContext created by ContextProviderCommandBuffer.

content/common/gpu/client/context_provider_command_buffer.cc

 // Copyright (c) 2013 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/context_provider_command_buffer.h"
 
 #include <set>
 #include <vector>
 
 #include "base/callback_helpers.h"
@@ skipping 116 matching lines @@
   return context3d_->GetContextSupport();
 }
 
 class GrContext* ContextProviderCommandBuffer::GrContext() {
   DCHECK(lost_context_callback_proxy_);  // Is bound to thread.
   DCHECK(context_thread_checker_.CalledOnValidThread());
 
   if (gr_context_)
     return gr_context_->get();
 
+  // If 3d context is lost, skip trying to make a GrContext which could fail.
+  if (IsContextLost())
+    return nullptr;
+
   gr_context_.reset(new GrContextForWebGraphicsContext3D(context3d_.get()));
 
-  // If GlContext is already lost, also abandon the new GrContext.
-  if (IsContextLost())
-    gr_context_->get()->abandonContext();
+  // GrContext creation should not fail with a valid context.

[piman, 2015/05/12 22:06:11]

I'm not sure that's true. IsContextLost() is fundamentally racy, the context
might be lost right after it returned false.

A lost context is still a usable c++ object with all methods being functional
(if only return errors and failing GL calls). Couldn't we do the same with
GrContext?

+  DCHECK(gr_context_->get());
 
   return gr_context_->get();
 }
 
 void ContextProviderCommandBuffer::SetupLock() {
   DCHECK(context3d_);
   context3d_->GetCommandBufferProxy()->SetLock(&context_lock_);
 }
 
 base::Lock* ContextProviderCommandBuffer::GetLock() {
@@ skipping 83 matching lines @@
 
 void ContextProviderCommandBuffer::SetMemoryPolicyChangedCallback(
     const MemoryPolicyChangedCallback& memory_policy_changed_callback) {
   DCHECK(context_thread_checker_.CalledOnValidThread());
   DCHECK(memory_policy_changed_callback_.is_null() ||
          memory_policy_changed_callback.is_null());
   memory_policy_changed_callback_ = memory_policy_changed_callback;
 }
 
 }  // namespace content