cc: Make async readback path use async glRreadPixels.

cc/test/pixel_test.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/test/pixel_test.h"
 
 #include "base/path_service.h"
+#include "base/run_loop.h"
 #include "cc/output/compositor_frame_metadata.h"
 #include "cc/output/gl_renderer.h"
 #include "cc/output/output_surface.h"
 #include "cc/resources/resource_provider.h"
 #include "cc/test/paths.h"
 #include "cc/test/pixel_test_utils.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gl/gl_implementation.h"
 #include "webkit/gpu/context_provider_in_process.h"
 #include "webkit/gpu/webgraphicscontext3d_in_process_command_buffer_impl.h"
@@ skipping 55 matching lines @@
 
   scoped_refptr<webkit::gpu::ContextProviderInProcess> offscreen_contexts =
       webkit::gpu::ContextProviderInProcess::Create();
   ASSERT_TRUE(offscreen_contexts->BindToCurrentThread());
   resource_provider_->set_offscreen_context_provider(offscreen_contexts);
 }
 
 bool PixelTest::RunPixelTest(RenderPassList* pass_list,
                              const base::FilePath& ref_file,
                              const PixelComparator& comparator) {
+  base::RunLoop run_loop;
+
   pass_list->back()->copy_callbacks.push_back(
-      base::Bind(&PixelTest::ReadbackResult, base::Unretained(this)));
+      base::Bind(&PixelTest::ReadbackResult,
+                 base::Unretained(this),
+                 run_loop.QuitClosure()));
 
   renderer_->DecideRenderPassAllocationsForFrame(*pass_list);
   renderer_->DrawFrame(pass_list);
 
-  // TODO(danakj): When the glReadPixels is async, wait for it to finish.
+  // Wait for the readback to complete.
+  output_surface_->context3d()->finish();
+  run_loop.Run();
 
   return PixelsMatchReference(ref_file, comparator);
 }
 
-void PixelTest::ReadbackResult(scoped_ptr<SkBitmap> bitmap) {
+void PixelTest::ReadbackResult(base::Closure quit_run_loop,
+                               scoped_ptr<SkBitmap> bitmap) {
   result_bitmap_ = bitmap.Pass();
+  quit_run_loop.Run();
 }
 
 bool PixelTest::PixelsMatchReference(const base::FilePath& ref_file,
                                      const PixelComparator& comparator) {
   base::FilePath test_data_dir;
   if (!PathService::Get(cc::DIR_TEST_DATA, &test_data_dir))
     return false;
 
   // If this is false, we didn't set up a readback on a render pass.
   if (!result_bitmap_)
     return false;
 
   // To rebaseline:
   // return WritePNGFile(*result_bitmap_, test_data_dir.Append(ref_file), true);
 
   return MatchesPNGFile(*result_bitmap_,
                         test_data_dir.Append(ref_file),
                         comparator);
 }
 
 }  // namespace cc