Add an integration test for the animation takeover path from cc to mt

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 735 matching lines @@
   void AfterTest() override {}
 
  private:
   FakeContentLayerClient client_;
   scoped_refptr<FakePictureLayer> scroll_layer_;
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(
     LayerTreeHostAnimationTestScrollOffsetChangesArePropagated);
 
+// Verifies that when a main thread scrolling reason gets added, the
+// notification to takover the animation on the main thread gets sent.
+class LayerTreeHostAnimationTestScrollOffsetAnimationTakeover
+    : public LayerTreeHostAnimationTest {
+ public:
+  LayerTreeHostAnimationTestScrollOffsetAnimationTakeover() {}
+
+  void SetupTree() override {
+    LayerTreeHostAnimationTest::SetupTree();
+
+    scroll_layer_ = FakePictureLayer::Create(&client_);
+    scroll_layer_->SetBounds(gfx::Size(10000, 10000));
+    client_.set_bounds(scroll_layer_->bounds());
+    scroll_layer_->SetScrollOffset(gfx::ScrollOffset(10, 20));
+    layer_tree_host()->root_layer()->AddChild(scroll_layer_);
+
+    AttachPlayersToTimeline();
+    player_child_->AttachLayer(scroll_layer_->id());
+    // Allows NotifyAnimationTakeover to get called.
+    player_child_->set_layer_animation_delegate(this);
+  }
+
+  void BeginTest() override { PostSetNeedsCommitToMainThread(); }
+
+  void DidCommit() override {
+    // Add a main thread scrolling reason after the first commit to trigger
+    // the takeover path.
+    if (layer_tree_host()->source_frame_number() == 1) {
+      scroll_layer_->AddMainThreadScrollingReasons(
+          MainThreadScrollingReason::kHasNonLayerViewportConstrainedObjects);
+    }
+  }
+
+  void WillCommitCompleteOnThread(LayerTreeHostImpl* host_impl) override {
+    bool have_animations = !host_impl->animation_host()
+                                ->active_element_animations_for_testing()
+                                .empty();
+    if (!have_animations) {

[ajuma, 2016/04/28 13:43:54]

Check host_impl->sync_tree()->source_frame_number() here, and only add the
animation when this is 1. 

[ymalik, 2016/04/28 14:23:45]

Confirmed with you that this should be 0. Done.

+      host_impl->animation_host()->ImplOnlyScrollAnimationCreate(
+          scroll_layer_->id(), gfx::ScrollOffset(650.f, 750.f),
+          gfx::ScrollOffset(10, 20));
+    }
+  }
+
+  void NotifyAnimationTakeover(base::TimeTicks monotonic_time,
+                               TargetProperty::Type target_property,
+                               double animation_start_time,
+                               std::unique_ptr<AnimationCurve> curve) override {
+    EndTest();
+  }
+
+  void AfterTest() override {}
+
+ private:
+  FakeContentLayerClient client_;
+  scoped_refptr<FakePictureLayer> scroll_layer_;
+};
+
+MULTI_THREAD_TEST_F(LayerTreeHostAnimationTestScrollOffsetAnimationTakeover);
+
 // Verifies that when the main thread removes a scroll animation and sets a new
 // scroll position, the active tree takes on exactly this new scroll position
 // after activation, and the main thread doesn't receive a spurious scroll
 // delta.
 class LayerTreeHostAnimationTestScrollOffsetAnimationRemoval
     : public LayerTreeHostAnimationTest {
  public:
   LayerTreeHostAnimationTestScrollOffsetAnimationRemoval()
       : final_postion_(50.0, 100.0) {}
 
@@ skipping 834 matching lines @@
  private:
   scoped_refptr<Layer> layer_;
   FakeContentLayerClient client_;
 };
 
 MULTI_THREAD_TEST_F(
     LayerTreeHostAnimationTestRebuildPropertyTreesOnAnimationSetNeedsCommit);
 
 }  // namespace
 }  // namespace cc