Revert of Remove CompositorObserver::OnCompositingEnded()

ui/views/controls/scroll_view_unittest.cc

 // Copyright (c) 2012 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 "ui/views/controls/scroll_view.h"
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/run_loop.h"
 #include "base/test/test_timeouts.h"
@@ skipping 250 matching lines @@
   }
 
  private:
   // ui::CompositorObserver:
   void OnCompositingDidCommit(ui::Compositor* compositor) override {
     quit_closure_.Run();
     quit_closure_.Reset();
   }
   void OnCompositingStarted(ui::Compositor* compositor,
                             base::TimeTicks start_time) override {}
+  void OnCompositingEnded(ui::Compositor* compositor) override {}
   void OnCompositingLockStateChanged(ui::Compositor* compositor) override {}
   void OnCompositingShuttingDown(ui::Compositor* compositor) override {}
 
   Widget* widget_ = nullptr;
 
   // Disable scrollbar hiding (i.e. disable overlay scrollbars) by default.
   bool use_overlay_scrollers_ = false;
 
   base::Closure quit_closure_;
 
@@ skipping 750 matching lines @@
   // Scroll via ScrollView API. Should be reflected on the impl side.
   offset.set_y(kDefaultHeight * 4);
   scroll_view->contents()->ScrollRectToVisible(offset);
   EXPECT_EQ(gfx::ScrollOffset(0, offset.y()), test_api.CurrentOffset());
 
   EXPECT_TRUE(compositor->GetScrollOffsetForLayer(layer_id, &impl_offset));
   EXPECT_EQ(gfx::ScrollOffset(0, offset.y()), impl_offset);
 }
 
 }  // namespace views