Add gfx::GpuMemoryBuffer::shared_memory_handle()

ui/gfx/gpu_memory_buffer.cc

Index: ui/gfx/gpu_memory_buffer.cc
diff --git a/ui/gfx/gpu_memory_buffer.cc b/ui/gfx/gpu_memory_buffer.cc
index e4e42434fabf9a5af5ab637e18ddee10768fdd13..3efb62de4e601487b7baffddb49c397b07946600 100644
--- a/ui/gfx/gpu_memory_buffer.cc
+++ b/ui/gfx/gpu_memory_buffer.cc
@@ -15,6 +15,10 @@ GpuMemoryBufferHandle::GpuMemoryBufferHandle(
 
 GpuMemoryBufferHandle::~GpuMemoryBufferHandle() {}
 
+base::SharedMemoryHandle GpuMemoryBuffer::shared_memory_handle() const {
+  return base::SharedMemoryHandle();
+}
+
 void GpuMemoryBuffer::SetColorSpaceForScanout(
     const gfx::ColorSpace& color_space) {}