Don't skip a frame when running smooth scroll animation on the main thread

third_party/WebKit/Source/platform/scroll/ScrollAnimatorTest.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 70 matching lines @@
     int visibleHeight() const override { return 768; }
     int visibleWidth() const override { return 1024; }
     bool scrollAnimatorEnabled() const override { return m_scrollAnimatorEnabled; }
     int pageStep(ScrollbarOrientation) const override { return 0; }
 
     void setScrollAnimator(ScrollAnimator* scrollAnimator)
     {
         animator = scrollAnimator;
     }
 
+    bool shouldScrollOnMainThread() const override
+    {
+        return m_scrollOnMainThread;
+    }
+
+    void setScrollOnMainThread(bool scrollOnMainThread)
+    {
+        m_scrollOnMainThread = scrollOnMainThread;
+    }
+
     DoublePoint scrollPositionDouble() const override
     {
         if (animator)
             return animator->currentPosition();
         return ScrollableArea::scrollPositionDouble();
     }
 
     void setScrollPosition(const DoublePoint& position, ScrollType type,
         ScrollBehavior behavior = ScrollBehaviorInstant)
     {
         if (animator)
             animator->setCurrentPosition(toFloatPoint(position));
         ScrollableArea::setScrollPosition(position, type, behavior);
     }
 
     DEFINE_INLINE_VIRTUAL_TRACE()
     {
         visitor->trace(animator);
         ScrollableArea::trace(visitor);
     }
 
 private:
     explicit MockScrollableArea(bool scrollAnimatorEnabled)
         : m_scrollAnimatorEnabled(scrollAnimatorEnabled) { }
 
     bool m_scrollAnimatorEnabled;
+    bool m_scrollOnMainThread = false;
     Member<ScrollAnimator> animator;
 };
 
 class TestScrollAnimator : public ScrollAnimator {
 public:
     TestScrollAnimator(ScrollableArea* scrollableArea, WTF::TimeFunction timingFunction)
         : ScrollAnimator(scrollableArea, timingFunction) {};
     ~TestScrollAnimator() override {};
 
     void setShouldSendToCompositor(bool send)
@@ skipping 23 matching lines @@
 static void reset(ScrollAnimator& scrollAnimator)
 {
     scrollAnimator.scrollToOffsetWithoutAnimation(FloatPoint());
 }
 
 // TODO(skobes): Add unit tests for composited scrolling paths.
 
 TEST(ScrollAnimatorTest, MainThreadStates)
 {
     MockScrollableArea* scrollableArea = MockScrollableArea::create(true);
+    scrollableArea->setScrollOnMainThread(true);
     ScrollAnimator* scrollAnimator = new ScrollAnimator(scrollableArea, getMockedTime);
 
     EXPECT_CALL(*scrollableArea, minimumScrollPosition()).Times(AtLeast(1))
         .WillRepeatedly(Return(IntPoint()));
     EXPECT_CALL(*scrollableArea, maximumScrollPosition()).Times(AtLeast(1))
         .WillRepeatedly(Return(IntPoint(1000, 1000)));
     EXPECT_CALL(*scrollableArea, setScrollOffset(_, _)).Times(2);
-    EXPECT_CALL(*scrollableArea, registerForAnimation()).Times(2);
+    // Once from userScroll.
+    EXPECT_CALL(*scrollableArea, registerForAnimation()).Times(1);
     EXPECT_CALL(*scrollableArea, scheduleAnimation()).Times(AtLeast(1))
         .WillRepeatedly(Return(true));
 
     // Idle
     EXPECT_FALSE(scrollAnimator->hasAnimationThatRequiresService());
     EXPECT_EQ(scrollAnimator->m_runState,
         ScrollAnimatorCompositorCoordinator::RunState::Idle);
 
     // WaitingToSendToCompositor
     scrollAnimator->userScroll(ScrollByLine, FloatSize(10, 0));
     EXPECT_EQ(scrollAnimator->m_runState,
-        ScrollAnimatorCompositorCoordinator::RunState::WaitingToSendToCompositor);
+        ScrollAnimatorCompositorCoordinator::RunState::RunningOnMainThread);
 
     // RunningOnMainThread
     gMockedTime += 0.05;
     scrollAnimator->updateCompositorAnimations();
     EXPECT_EQ(scrollAnimator->m_runState,
         ScrollAnimatorCompositorCoordinator::RunState::RunningOnMainThread);
     scrollAnimator->tickAnimation(getMockedTime());
     EXPECT_EQ(scrollAnimator->m_runState,
         ScrollAnimatorCompositorCoordinator::RunState::RunningOnMainThread);
 
     // PostAnimationCleanup
     scrollAnimator->cancelAnimation();
     EXPECT_EQ(scrollAnimator->m_runState,
         ScrollAnimatorCompositorCoordinator::RunState::PostAnimationCleanup);
 
     // Idle
     scrollAnimator->updateCompositorAnimations();
     scrollAnimator->tickAnimation(getMockedTime());
     EXPECT_EQ(scrollAnimator->m_runState,
         ScrollAnimatorCompositorCoordinator::RunState::Idle);
 
     reset(*scrollAnimator);
+
+    // Forced GC in order to finalize objects depending on the mock object.
+    ThreadHeap::collectAllGarbage();
 }
 
 TEST(ScrollAnimatorTest, MainThreadEnabled)
 {
     MockScrollableArea* scrollableArea = MockScrollableArea::create(true);
     ScrollAnimator* scrollAnimator = new ScrollAnimator(scrollableArea, getMockedTime);
 
     EXPECT_CALL(*scrollableArea, minimumScrollPosition()).Times(AtLeast(1)).WillRepeatedly(Return(IntPoint()));
     EXPECT_CALL(*scrollableArea, maximumScrollPosition()).Times(AtLeast(1)).WillRepeatedly(Return(IntPoint(1000, 1000)));
     EXPECT_CALL(*scrollableArea, setScrollOffset(_, _)).Times(9);
@@ skipping 411 matching lines @@
     animator->updateCompositorAnimations();
     animator->tickAnimation(getMockedTime());
     EXPECT_EQ(FloatPoint(110, 90), animator->currentPosition());
     reset(*animator);
 
     // Forced GC in order to finalize objects depending on the mock object.
     ThreadHeap::collectAllGarbage();
 }
 
 } // namespace blink