Add gfx::GpuMemoryBuffer::shared_memory_handle()

gpu/ipc/client/gpu_memory_buffer_impl_shared_memory_unittest.cc

 // Copyright 2015 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 <memory>
 
 #include "gpu/ipc/client/gpu_memory_buffer_impl_shared_memory.h"
 #include "gpu/ipc/client/gpu_memory_buffer_impl_test_template.h"
 
 namespace gpu {
@@ skipping 14 matching lines @@
 
   for (auto format : gfx::GetBufferFormatsForTesting()) {
     bool destroyed = false;
     std::unique_ptr<GpuMemoryBufferImplSharedMemory> buffer(
         GpuMemoryBufferImplSharedMemory::Create(
             kBufferId, buffer_size, format,
             base::Bind(&BufferDestroyed, base::Unretained(&destroyed))));
     ASSERT_TRUE(buffer);
     EXPECT_EQ(buffer->GetFormat(), format);
 
+    // Check if the backend is actually SharedMemory and its GUID is available.
+    EXPECT_NE(base::UnguessableToken(),
+              buffer->shared_memory_handle().GetGUID());
+
     // Check if destruction callback is executed when deleting the buffer.
     buffer.reset();
     ASSERT_TRUE(destroyed);
   }
 }
 
 }  // namespace
 }  // namespace gpu