Fix nullptr-deref when command buffer init fails

content/common/gpu/gpu_command_buffer_stub.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 "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/hash.h"
 #include "base/json/json_writer.h"
 #include "base/memory/shared_memory.h"
@@ skipping 411 matching lines @@
     OnRetireSyncPoint(sync_points_.front());
 
   if (decoder_)
     decoder_->set_engine(NULL);
 
   // The scheduler has raw references to the decoder and the command buffer so
   // destroy it before those.
   scheduler_.reset();
 
   bool have_context = false;
-  if (decoder_) {
+  if (decoder_ && decoder_->GetGLContext()) {
     // Try to make the context current regardless of whether it was lost, so we
     // don't leak resources.
     have_context = decoder_->GetGLContext()->MakeCurrent(surface_.get());
   }
   FOR_EACH_OBSERVER(DestructionObserver,
                     destruction_observers_,
                     OnWillDestroyStub());
 
   if (decoder_) {
     decoder_->Destroy(have_context);
@@ skipping 669 matching lines @@
   Send(new GpuCommandBufferMsg_SwapBuffersCompleted(route_id_, latency_info));
 }
 
 void GpuCommandBufferStub::SendUpdateVSyncParameters(base::TimeTicks timebase,
                                                      base::TimeDelta interval) {
   Send(new GpuCommandBufferMsg_UpdateVSyncParameters(route_id_, timebase,
                                                      interval));
 }
 
 }  // namespace content