Refactor gpu::Buffer to allow different types of backing

mojo/services/gles2/command_buffer_impl.cc

Index: mojo/services/gles2/command_buffer_impl.cc
diff --git a/mojo/services/gles2/command_buffer_impl.cc b/mojo/services/gles2/command_buffer_impl.cc
index 1e8a4f6e1d1132efeff343cbdd5fcb5aa32b7078..7d33b722cd8ddb24fc0fab5e4a392fa0b4698643 100644
--- a/mojo/services/gles2/command_buffer_impl.cc
+++ b/mojo/services/gles2/command_buffer_impl.cc
@@ -118,11 +118,14 @@ bool CommandBufferImpl::DoInitialize(const ShmHandle& shared_state) {
 
   // TODO(piman): other callbacks
 
+  const size_t kSize = sizeof(gpu::CommandBufferSharedState);
   scoped_ptr<base::SharedMemory> shared_state_shm(
       new base::SharedMemory(shared_state, false));
-  if (!command_buffer_->SetSharedStateBuffer(shared_state_shm.Pass()))
+  if (!shared_state_shm->Map(kSize))
     return false;
 
+  command_buffer_->SetSharedStateBuffer(
+      gpu::MakeBackingFromSharedMemory(shared_state_shm.Pass(), kSize));
   return true;
 }
 
@@ -152,7 +155,8 @@ void CommandBufferImpl::RegisterTransferBuffer(int32_t id,
     return;
   }
 
-  command_buffer_->RegisterTransferBuffer(id, shared_memory.Pass(), size);
+  command_buffer_->RegisterTransferBuffer(
+      id, gpu::MakeBackingFromSharedMemory(shared_memory.Pass(), size));
 }
 
 void CommandBufferImpl::DestroyTransferBuffer(int32_t id) {