cc: Make LayerTreeHostImpl::SwapBuffers not virtual.

cc/trees/layer_tree_host_unittest_animation.cc

 // Copyright 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 "cc/trees/layer_tree_host.h"
 
 #include <stdint.h>
 
 #include "cc/animation/animation_curve.h"
 #include "cc/animation/animation_host.h"
@@ skipping 1320 matching lines @@
         AddAnimatedTransformToPlayer(player_.get(), 0.1, 5, 5);
         break;
       case 2:
         // Second frame: add an animation to the content layer. The root layer
         // animation has caused us to animate already during this frame.
         AddOpacityTransitionToPlayer(player_child_.get(), 0.1, 5, 5, false);
         break;
     }
   }
 
-  void SwapBuffersOnThread(LayerTreeHostImpl* host_impl, bool result) override {
+  void DrawLayersOnThread(LayerTreeHostImpl* host_impl) override {
     // After both animations have started, verify that they have valid
     // start times.
     if (host_impl->active_tree()->source_frame_number() < 2)
       return;
+
+    // Animation state is updated after drawing.

[danakj, 2016/07/13 21:50:18]

This one is a bit awk. ProxyImpl does Draw -> UpdateAnimationState -> Swap.

In the future I guess it'll be just Draw -> UpdateAnimationState. So we need to
do this CheckAnimations work after the update somehow. I used a post-task.
SeemsGood?

+    ImplThreadTaskRunner()->PostTask(
+        FROM_HERE,
+        base::Bind(&LayerTreeHostAnimationTestAddAnimationAfterAnimating::
+                       CheckAnimations,
+                   base::Unretained(this), host_impl));
+  }
+
+  void CheckAnimations(LayerTreeHostImpl* host_impl) {
     AnimationHost::ElementToAnimationsMap element_animations_copy =
         host_impl->animation_host()->active_element_animations_for_testing();
     EXPECT_EQ(2u, element_animations_copy.size());
     for (auto& it : element_animations_copy) {
       ElementId id = it.first;
       if (id ==
           host_impl->active_tree()->root_layer_for_testing()->element_id()) {
         Animation* anim = it.second->GetAnimation(TargetProperty::TRANSFORM);
         EXPECT_GT((anim->start_time() - base::TimeTicks()).InSecondsF(), 0);
       } else if (id == layer_->element_id()) {
@@ skipping 489 matching lines @@
  private:
   scoped_refptr<Layer> layer_;
   FakeContentLayerClient client_;
 };
 
 MULTI_THREAD_TEST_F(
     LayerTreeHostAnimationTestRebuildPropertyTreesOnAnimationSetNeedsCommit);
 
 }  // namespace
 }  // namespace cc