exo: Directly create GpuMemoryBufferImpl when a handle is available.

gpu/ipc/client/gpu_memory_buffer_impl.cc

 // Copyright 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 "gpu/ipc/client/gpu_memory_buffer_impl.h"
 
 #include "base/logging.h"
 #include "build/build_config.h"
 #include "gpu/ipc/client/gpu_memory_buffer_impl_shared_memory.h"
 
@@ skipping 12 matching lines @@
                                          gfx::BufferFormat format,
                                          const DestructionCallback& callback)
     : id_(id),
       size_(size),
       format_(format),
       callback_(callback),
       mapped_(false) {}
 
 GpuMemoryBufferImpl::~GpuMemoryBufferImpl() {
   DCHECK(!mapped_);
-  callback_.Run(destruction_sync_token_);
+  if (!callback_.is_null())
+    callback_.Run(destruction_sync_token_);
 }
 
 // static
 std::unique_ptr<GpuMemoryBufferImpl> GpuMemoryBufferImpl::CreateFromHandle(
     const gfx::GpuMemoryBufferHandle& handle,
     const gfx::Size& size,
     gfx::BufferFormat format,
     gfx::BufferUsage usage,
     const DestructionCallback& callback) {
   switch (handle.type) {
@@ skipping 26 matching lines @@
 
 gfx::GpuMemoryBufferId GpuMemoryBufferImpl::GetId() const {
   return id_;
 }
 
 ClientBuffer GpuMemoryBufferImpl::AsClientBuffer() {
   return reinterpret_cast<ClientBuffer>(this);
 }
 
 }  // namespace gpu