cc: Make OutputSurface::SwapBuffers pure virtual

cc/output/output_surface_unittest.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/output_surface.h"
 
 #include "base/test/test_simple_task_runner.h"
 #include "cc/output/managed_memory_policy.h"
 #include "cc/output/output_surface_client.h"
 #include "cc/output/software_output_device.h"
@@ skipping 14 matching lines @@
   explicit TestOutputSurface(scoped_refptr<ContextProvider> context_provider)
       : OutputSurface(context_provider) {}
 
   explicit TestOutputSurface(scoped_ptr<SoftwareOutputDevice> software_device)
       : OutputSurface(software_device.Pass()) {}
 
   TestOutputSurface(scoped_refptr<ContextProvider> context_provider,
                     scoped_ptr<SoftwareOutputDevice> software_device)
       : OutputSurface(context_provider, software_device.Pass()) {}
 
+  virtual void SwapBuffers(CompositorFrame* frame) override {
+    client_->DidSwapBuffers();
+    client_->DidSwapBuffersComplete();
+  }
+
   bool InitializeNewContext3d(
       scoped_refptr<ContextProvider> new_context_provider) {
     return InitializeAndSetContext3d(new_context_provider);
   }
 
   using OutputSurface::ReleaseGL;
 
   void CommitVSyncParametersForTesting(base::TimeTicks timebase,
                                        base::TimeDelta interval) {
     CommitVSyncParameters(timebase, interval);
@@ skipping 173 matching lines @@
   EXPECT_EQ(1, software_output_device->ensure_backbuffer_count());
   EXPECT_EQ(0, software_output_device->discard_backbuffer_count());
   output_surface.DiscardBackbuffer();
 
   EXPECT_EQ(1, software_output_device->ensure_backbuffer_count());
   EXPECT_EQ(1, software_output_device->discard_backbuffer_count());
 }
 
 }  // namespace
 }  // namespace cc