[cc] cleanup worklet animation tests

- Move two tests for AnimationHost/WorkletAnimation interactions to animation_host_unittests
- Remove unnecessary complexity related to creating and testing an impl instance.
  These tests don't need to distinguish between main/impl instances at all.

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I928e664ddf4fab8496fbbe3a09fcdcd120c875fb
Reviewed-on: https://chromium-review.googlesource.com/1133770Reviewed-by: Stephen McGruer <smcgruer@chromium.org>
Commit-Queue: Majid Valipour <majidvp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578405}

cc/animation/animation_host_unittest.cc

@@ -183,5 +183,60 @@ TEST_F(AnimationHostTest, LayerTreeMutatorUpdateTakesEffectInSameFrame) {
       element_id_, ElementListType::ACTIVE, expected_opacity);
 }
 
+TEST_F(AnimationHostTest, LayerTreeMutatorsIsMutatedWithCorrectInputState) {
+  AttachWorkletAnimation();
+
+  MockLayerTreeMutator* mock_mutator = new NiceMock<MockLayerTreeMutator>();
+  host_impl_->SetLayerTreeMutator(
+      base::WrapUnique<LayerTreeMutator>(mock_mutator));
+  ON_CALL(*mock_mutator, HasAnimators()).WillByDefault(Return(true));
+
+  const float start_opacity = .7f;
+  const float end_opacity = .3f;
+  const double duration = 1.;
+
+  AddOpacityTransitionToAnimation(worklet_animation_.get(), duration,
+                                  start_opacity, end_opacity, true);
+
+  host_->PushPropertiesTo(host_impl_);
+  host_impl_->ActivateAnimations();
+
+  EXPECT_CALL(*mock_mutator, MutateRef(_));
+
+  base::TimeTicks time;
+  time += base::TimeDelta::FromSecondsD(0.1);
+  TickAnimationsTransferEvents(time, 0u);
+}
+
+TEST_F(AnimationHostTest, LayerTreeMutatorsIsMutatedOnlyWhenInputChanges) {
+  AttachWorkletAnimation();
+
+  MockLayerTreeMutator* mock_mutator = new NiceMock<MockLayerTreeMutator>();
+  host_impl_->SetLayerTreeMutator(
+      base::WrapUnique<LayerTreeMutator>(mock_mutator));
+  ON_CALL(*mock_mutator, HasAnimators()).WillByDefault(Return(true));
+
+  const float start_opacity = .7f;
+  const float end_opacity = .3f;
+  const double duration = 1.;
+
+  AddOpacityTransitionToAnimation(worklet_animation_.get(), duration,
+                                  start_opacity, end_opacity, true);
+
+  host_->PushPropertiesTo(host_impl_);
+  host_impl_->ActivateAnimations();
+
+  EXPECT_CALL(*mock_mutator, MutateRef(_)).Times(1);
+
+  base::TimeTicks time;
+  time += base::TimeDelta::FromSecondsD(0.1);
+  TickAnimationsTransferEvents(time, 0u);
+
+  // The time has not changed which means worklet animation input is the same.
+  // Ticking animations again should not result in mutator being asked to
+  // mutate.
+  TickAnimationsTransferEvents(time, 0u);
+}
+
 }  // namespace
 }  // namespace cc