Use observer pattern instead of sniffing SwapCompositorFrame IPC

content/browser/renderer_host/input/composited_scrolling_browsertest.cc

 // Copyright 2015 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 <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "base/run_loop.h"
@@ skipping 65 matching lines @@
     EXPECT_EQ(SyntheticGesture::GESTURE_FINISHED, result);
     runner_->Quit();
   }
 
  protected:
   void LoadURL() {
     const GURL data_url(kCompositedScrollingDataURL);
     NavigateToURL(shell(), data_url);
 
     RenderWidgetHostImpl* host = GetWidgetHost();
-    scoped_refptr<FrameWatcher> frame_watcher(new FrameWatcher());
-    frame_watcher->AttachTo(shell()->web_contents());
+    FrameWatcher frame_watcher(shell()->web_contents());
     host->GetView()->SetSize(gfx::Size(400, 400));
 
     base::string16 ready_title(base::ASCIIToUTF16("ready"));
     TitleWatcher watcher(shell()->web_contents(), ready_title);
     ignore_result(watcher.WaitAndGetTitle());
 
     // We need to wait until at least one frame has been composited
     // otherwise the injection of the synthetic gestures may get
     // dropped because of MainThread/Impl thread sync of touch event
     // regions.
-    frame_watcher->WaitFrames(1);
+    frame_watcher.WaitFrames(1);
   }
 
   // ContentBrowserTest:
   int ExecuteScriptAndExtractInt(const std::string& script) {
     int value = 0;
     EXPECT_TRUE(content::ExecuteScriptAndExtractInt(
         shell(), "domAutomationController.send(" + script + ")", &value));
     return value;
   }
 
@@ skipping 51 matching lines @@
                        MAYBE_Scroll3DTransformedScroller) {
   LoadURL();
   int scrollDistance =
       DoTouchScroll(gfx::Point(50, 150), gfx::Vector2d(0, 100));
   // The scroll distance is increased due to the rotation of the scroller.
   EXPECT_EQ(std::floor(100 / std::cos(cc::MathUtil::Deg2Rad(30.f))) - 1,
             scrollDistance);
 }
 
 }  // namespace content