Add gpu::MailboxHolder to hold state for a gpu::Mailbox

cc/trees/layer_tree_host_unittest_copyrequest.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 "cc/output/copy_output_request.h"
 #include "cc/output/copy_output_result.h"
 #include "cc/test/fake_content_layer.h"
 #include "cc/test/fake_content_layer_client.h"
 #include "cc/test/fake_output_surface.h"
 #include "cc/test/layer_tree_test.h"
@@ skipping 788 matching lines @@
     // Request a copy to a provided texture. This should not create a new
     // texture.
     scoped_ptr<CopyOutputRequest> request =
         CopyOutputRequest::CreateRequest(base::Bind(
             &LayerTreeHostCopyRequestTestProvideTexture::CopyOutputCallback,
             base::Unretained(this)));
 
     gpu::Mailbox mailbox;
     external_context_provider_->Context3d()->genMailboxCHROMIUM(mailbox.name);
     sync_point_ = external_context_provider_->Context3d()->insertSyncPoint();
-    request->SetTextureMailbox(TextureMailbox(mailbox, sync_point_));
+    request->SetTextureMailbox(
+        TextureMailbox(mailbox, GL_TEXTURE_2D, sync_point_));
     EXPECT_TRUE(request->has_texture_mailbox());
 
     copy_layer_->RequestCopyOfOutput(request.Pass());
   }
 
   virtual void AfterTest() OVERRIDE {
     // Expect the compositor to have waited for the sync point in the provided
     // TextureMailbox.
     EXPECT_EQ(sync_point_, waited_sync_point_after_readback_);
     // Except the copy to have *not* made another texture.
     EXPECT_EQ(num_textures_without_readback_, num_textures_with_readback_);
   }
 
   scoped_refptr<TestContextProvider> external_context_provider_;
   unsigned sync_point_;
 };
 
 SINGLE_AND_MULTI_THREAD_DIRECT_RENDERER_NOIMPL_TEST_F(
     LayerTreeHostCopyRequestTestProvideTexture);
 
 }  // namespace
 }  // namespace cc