Use observer pattern instead of sniffing SwapCompositorFrame IPC

content/browser/renderer_host/input/non_blocking_event_browsertest.cc

 // Copyright 2016 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/auto_reset.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/macros.h"
@@ skipping 109 matching lines @@
     return ExecuteScriptAndExtractInt("document.scrollingElement.scrollTop");
   }
 
   void DoWheelScroll() {
     EXPECT_EQ(0, GetScrollTop());
 
     int scrollHeight =
         ExecuteScriptAndExtractInt("document.documentElement.scrollHeight");
     EXPECT_EQ(kWebsiteHeight, scrollHeight);
 
-    scoped_refptr<FrameWatcher> frame_watcher(new FrameWatcher());
-    frame_watcher->AttachTo(shell()->web_contents());
+    FrameWatcher frame_watcher(shell()->web_contents());
     scoped_refptr<InputMsgWatcher> input_msg_watcher(
         new InputMsgWatcher(GetWidgetHost(), blink::WebInputEvent::MouseWheel));
 
     GetWidgetHost()->ForwardWheelEvent(
         SyntheticWebMouseWheelEventBuilder::Build(10, 10, 0, -53, 0, true));
 
     // Runs until we get the InputMsgAck callback
     EXPECT_EQ(INPUT_EVENT_ACK_STATE_SET_NON_BLOCKING,
               input_msg_watcher->WaitForAck());
 
     // Expect that the compositor scrolled at least one pixel while the
     // main thread was in a busy loop.
-    while (frame_watcher->LastMetadata().root_scroll_offset.y() <= 0)
-      frame_watcher->WaitFrames(1);
+    while (frame_watcher.LastMetadata().root_scroll_offset.y() <= 0)
+      frame_watcher.WaitFrames(1);
   }
 
   void DoTouchScroll() {
     EXPECT_EQ(0, GetScrollTop());
 
     int scrollHeight =
         ExecuteScriptAndExtractInt("document.documentElement.scrollHeight");
     EXPECT_EQ(kWebsiteHeight, scrollHeight);
 
-    scoped_refptr<FrameWatcher> frame_watcher(new FrameWatcher());
-    frame_watcher->AttachTo(shell()->web_contents());
+    FrameWatcher frame_watcher(shell()->web_contents());
 
     SyntheticSmoothScrollGestureParams params;
     params.gesture_source_type = SyntheticGestureParams::TOUCH_INPUT;
     params.anchor = gfx::PointF(50, 50);
     params.distances.push_back(gfx::Vector2d(0, -45));
 
     std::unique_ptr<SyntheticSmoothScrollGesture> gesture(
         new SyntheticSmoothScrollGesture(params));
     GetWidgetHost()->QueueSyntheticGesture(
         std::move(gesture),
         base::Bind(&NonBlockingEventBrowserTest::OnSyntheticGestureCompleted,
                    base::Unretained(this)));
 
     // Expect that the compositor scrolled at least one pixel while the
     // main thread was in a busy loop.
-    while (frame_watcher->LastMetadata().root_scroll_offset.y() <= 0)
-      frame_watcher->WaitFrames(1);
+    while (frame_watcher.LastMetadata().root_scroll_offset.y() <= 0)
+      frame_watcher.WaitFrames(1);
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NonBlockingEventBrowserTest);
 };
 
 IN_PROC_BROWSER_TEST_F(NonBlockingEventBrowserTest, MouseWheel) {
   LoadURL(kNonBlockingEventDataURL);
   DoWheelScroll();
 }
@@ skipping 17 matching lines @@
 #define MAYBE_PassiveTouchStartBlockingTouchEnd \
   PassiveTouchStartBlockingTouchEnd
 #endif
 IN_PROC_BROWSER_TEST_F(NonBlockingEventBrowserTest,
                        MAYBE_PassiveTouchStartBlockingTouchEnd) {
   LoadURL(kPassiveTouchStartBlockingTouchEndDataURL);
   DoTouchScroll();
 }
 
 }  // namespace content