Fix callback layer animation observer logic

If all the sequences has been detached, the observer should be notified,
otherwise it might wait forever.

Also added unit test cases for this scenario.

Bug: b/141997678
Test: Run CallbackLayerAnimationObserverTest.* in compositor_unittests
Change-Id: I3a025de8e635a383910ef4a3e650683478e8d3fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1938459Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: Yue Li <updowndota@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721580}

ui/compositor/callback_layer_animation_observer.cc

@@ -92,6 +92,8 @@ void CallbackLayerAnimationObserver::OnDetachedFromSequence(
     ui::LayerAnimationSequence* sequence) {
   CHECK_LT(detached_sequence_count_, attached_sequence_count_);
   ++detached_sequence_count_;
+  CheckAllSequencesStarted();
+  CheckAllSequencesCompleted();
 }
 
 int CallbackLayerAnimationObserver::GetNumSequencesCompleted() {
@@ -99,12 +101,14 @@ int CallbackLayerAnimationObserver::GetNumSequencesCompleted() {
 }
 
 void CallbackLayerAnimationObserver::CheckAllSequencesStarted() {
-  if (active_ && attached_sequence_count_ == started_count_)
+  if (active_ && (attached_sequence_count_ == started_count_ ||
+                  detached_sequence_count_ == attached_sequence_count_))
     animation_started_callback_.Run(*this);
 }
 
 void CallbackLayerAnimationObserver::CheckAllSequencesCompleted() {
-  if (active_ && GetNumSequencesCompleted() == attached_sequence_count_) {
+  if (active_ && (GetNumSequencesCompleted() == attached_sequence_count_ ||
+                  detached_sequence_count_ == attached_sequence_count_)) {
     active_ = false;
     base::WeakPtr<CallbackLayerAnimationObserver> weak_this =
         weak_factory_.GetWeakPtr();

ui/compositor/callback_layer_animation_observer_unittest.cc

@@ -641,5 +641,42 @@ TEST_F(CallbackLayerAnimationObserverTest,
   EXPECT_EQ(4, observer_->successful_count());
 }
 
+TEST_F(CallbackLayerAnimationObserverTest, DetachBeforeActive) {
+  LayerAnimationSequence* sequence_1 = CreateLayerAnimationSequence();
+  LayerAnimationSequence* sequence_2 = CreateLayerAnimationSequence();
+
+  observer_test_api_->AttachedToSequence(sequence_1);
+  observer_test_api_->AttachedToSequence(sequence_2);
+  observer_->OnLayerAnimationStarted(sequence_1);
+  observer_->OnLayerAnimationEnded(sequence_1);
+  observer_test_api_->DetachedFromSequence(sequence_1, true);
+  observer_test_api_->DetachedFromSequence(sequence_2, true);
+
+  observer_->SetActive();
+
+  EXPECT_FALSE(observer_->active());
+  EXPECT_TRUE(callbacks_->animations_started());
+  EXPECT_TRUE(callbacks_->animations_ended());
+}
+
+TEST_F(CallbackLayerAnimationObserverTest, DetachAfterActive) {
+  LayerAnimationSequence* sequence_1 = CreateLayerAnimationSequence();
+  LayerAnimationSequence* sequence_2 = CreateLayerAnimationSequence();
+
+  observer_test_api_->AttachedToSequence(sequence_1);
+  observer_test_api_->AttachedToSequence(sequence_2);
+
+  observer_->SetActive();
+
+  observer_->OnLayerAnimationStarted(sequence_1);
+  observer_->OnLayerAnimationEnded(sequence_1);
+  observer_test_api_->DetachedFromSequence(sequence_1, true);
+  observer_test_api_->DetachedFromSequence(sequence_2, true);
+
+  EXPECT_FALSE(observer_->active());
+  EXPECT_TRUE(callbacks_->animations_started());
+  EXPECT_TRUE(callbacks_->animations_ended());
+}
+
 }  // namespace test
 }  // namespace ui