[animation-worklet] Do not tick worklet animations on main thread

We should not tick cc:WorkletAnimation on main thread. The local
time is actually not updated on main thread so the produced value
is incorrect and more importantly causes superfluous commits.


Note: We may decide to avoid ticking all animations on main thread
(See http://crbug.com/762717) in which case we can remove this.


TEST: cc/animation/worklet_animation_unittest.cc
Bug: 839555

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I3335bfd452cc284a585e84a87b8912207b843813
Reviewed-on: https://chromium-review.googlesource.com/1042875
Commit-Queue: Majid Valipour <majidvp@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556256}

cc/animation/worklet_animation.cc

@@ -11,11 +11,13 @@ namespace cc {
 WorkletAnimation::WorkletAnimation(
     int id,
     const std::string& name,
-    std::unique_ptr<ScrollTimeline> scroll_timeline)
+    std::unique_ptr<ScrollTimeline> scroll_timeline,
+    bool is_controlling_instance)
     : SingleKeyframeEffectAnimation(id),
       name_(name),
       scroll_timeline_(std::move(scroll_timeline)),
-      last_current_time_(base::nullopt) {}
+      last_current_time_(base::nullopt),
+      is_impl_instance_(is_controlling_instance) {}
 
 WorkletAnimation::~WorkletAnimation() = default;
 
@@ -24,7 +26,7 @@ scoped_refptr<WorkletAnimation> WorkletAnimation::Create(
     const std::string& name,
     std::unique_ptr<ScrollTimeline> scroll_timeline) {
   return WrapRefCounted(
-      new WorkletAnimation(id, name, std::move(scroll_timeline)));
+      new WorkletAnimation(id, name, std::move(scroll_timeline), false));
 }
 
 scoped_refptr<Animation> WorkletAnimation::CreateImplInstance() const {
@@ -33,7 +35,7 @@ scoped_refptr<Animation> WorkletAnimation::CreateImplInstance() const {
     impl_timeline = scroll_timeline_->CreateImplInstance();
 
   return WrapRefCounted(
-      new WorkletAnimation(id(), name(), std::move(impl_timeline)));
+      new WorkletAnimation(id(), name(), std::move(impl_timeline), true));
 }
 
 void WorkletAnimation::SetLocalTime(base::TimeDelta local_time) {
@@ -42,6 +44,10 @@ void WorkletAnimation::SetLocalTime(base::TimeDelta local_time) {
 }
 
 void WorkletAnimation::Tick(base::TimeTicks monotonic_time) {
+  // Do not tick worklet animations on main thread. This should be removed if we
+  // skip ticking all animations on main thread in http://crbug.com/762717.
+  if (!is_impl_instance_)
+    return;
   // As the output of a WorkletAnimation is driven by a script-provided local
   // time, we don't want the underlying effect to participate in the normal
   // animations lifecycle. To avoid this we pause the underlying keyframe effect

cc/animation/worklet_animation.h

@@ -23,7 +23,8 @@ class CC_ANIMATION_EXPORT WorkletAnimation final
  public:
   WorkletAnimation(int id,
                    const std::string& name,
-                   std::unique_ptr<ScrollTimeline> scroll_timeline);
+                   std::unique_ptr<ScrollTimeline> scroll_timeline,
+                   bool is_controlling_instance);
   static scoped_refptr<WorkletAnimation> Create(
       int id,
       const std::string& name,
@@ -66,6 +67,8 @@ class CC_ANIMATION_EXPORT WorkletAnimation final
   base::TimeDelta local_time_;
 
   base::Optional<double> last_current_time_;
+
+  bool is_impl_instance_;
 };
 
 }  // namespace cc

cc/animation/worklet_animation_unittest.cc

@@ -75,6 +75,10 @@ TEST_F(WorkletAnimationTest, LocalTimeIsUsedWithAnimations) {
   worklet_animation_impl_->SetLocalTime(local_time);
 
   TickAnimationsTransferEvents(base::TimeTicks(), 0u);
+
+  TestLayer* layer =
+      client_.FindTestLayer(element_id_, ElementListType::ACTIVE);
+  EXPECT_FALSE(layer->is_property_mutated(TargetProperty::OPACITY));
   client_impl_.ExpectOpacityPropertyMutated(
       element_id_, ElementListType::ACTIVE, expected_opacity);
 }