Add gpu::BufferBacking::shared_memory_handle()

gpu/command_buffer/common/buffer.h

Index: gpu/command_buffer/common/buffer.h
diff --git a/gpu/command_buffer/common/buffer.h b/gpu/command_buffer/common/buffer.h
index d4de9175471160c9cd478e690978d50b0d207764..6a0a0d28ef2d73d14984115970a46f2882ec0c65 100644
--- a/gpu/command_buffer/common/buffer.h
+++ b/gpu/command_buffer/common/buffer.h
@@ -17,8 +17,11 @@
 #include "gpu/gpu_export.h"
 
 namespace base {
-  class SharedMemory;
-}
+
+class SharedMemory;
+class SharedMemoryHandle;
+
+}  // namespace base
 
 namespace gpu {
 
@@ -26,6 +29,7 @@ class GPU_EXPORT BufferBacking {
  public:
   virtual ~BufferBacking() {}
   virtual bool is_shared() const;
+  virtual base::SharedMemoryHandle shared_memory_handle() const;
   virtual void* GetMemory() const = 0;
   virtual size_t GetSize() const = 0;
 };
@@ -36,6 +40,7 @@ class GPU_EXPORT SharedMemoryBufferBacking : public BufferBacking {
                             size_t size);
   ~SharedMemoryBufferBacking() override;
   bool is_shared() const override;
+  base::SharedMemoryHandle shared_memory_handle() const override;
   void* GetMemory() const override;
   size_t GetSize() const override;
   base::SharedMemory* shared_memory() { return shared_memory_.get(); }