Smooth scroll animation should not override scroll anchoring update (MT)

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

 /*
  * Copyright (c) 2011, 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 55 matching lines @@
     , m_lastGranularity(ScrollByPixel)
 {
 }
 
 ScrollAnimator::~ScrollAnimator()
 {
 }
 
 FloatPoint ScrollAnimator::desiredTargetPosition() const
 {
+    if (m_runState == RunState::WaitingToCancelOnCompositor)
+        return currentPosition();
     return (m_animationCurve || m_runState == RunState::WaitingToSendToCompositor)
         ? m_targetOffset : currentPosition();
 }
 
 bool ScrollAnimator::hasRunningAnimation() const
 {
     return (m_animationCurve || m_runState == RunState::WaitingToSendToCompositor);
 }
 
 FloatSize ScrollAnimator::computeDeltaToConsume(const FloatSize& delta) const
@@ skipping 55 matching lines @@
     // animation rather than animating multiple scrollers at the same time.
     return ScrollResult(false, false, delta.width(), delta.height());
 }
 
 bool ScrollAnimator::willAnimateToOffset(const FloatPoint& targetPos)
 {
     if (m_runState == RunState::PostAnimationCleanup)
         resetAnimationState();
 
     if (m_runState == RunState::WaitingToCancelOnCompositor) {
-        // Ignore user scroll if WaitingToCancelOnCompositor. Can be in this
-        // state when holding down an arrow.
-        // TODO(ymalik): Handle this case by either updating the target on the
-        // current scroll or starting a new animation (see crbug.com/599876).
+        ASSERT(m_animationCurve);
+        m_targetOffset = targetPos;
+        if (registerAndScheduleAnimation())
+            m_runState = RunState::WaitingToCancelOnCompositorButNewScroll;
         return true;
     }
 
     if (m_animationCurve) {
         if ((targetPos - m_targetOffset).isZero())
             return true;
 
         m_targetOffset = targetPos;
         ASSERT(m_runState == RunState::RunningOnMainThread
             || m_runState == RunState::RunningOnCompositor
@@ skipping 99 matching lines @@
 }
 
 void ScrollAnimator::updateCompositorAnimations()
 {
     if (m_runState == RunState::PostAnimationCleanup) {
         postAnimationCleanupAndReset();
         return;
     }
 
     if (m_compositorAnimationId && m_runState != RunState::RunningOnCompositor
-        && m_runState != RunState::RunningOnCompositorButNeedsUpdate) {
+        && m_runState != RunState::RunningOnCompositorButNeedsUpdate
+        && m_runState != RunState::WaitingToCancelOnCompositorButNewScroll) {
         // If the current run state is WaitingToSendToCompositor but we have a
         // non-zero compositor animation id, there's a currently running
         // compositor animation that needs to be removed here before the new
         // animation is added below.
         ASSERT(m_runState == RunState::WaitingToCancelOnCompositor
             || m_runState == RunState::WaitingToSendToCompositor
             || m_runState == RunState::RunningOnCompositorButNeedsTakeover);
 
         if (m_runState == RunState::RunningOnCompositorButNeedsTakeover) {
             // The animation is already aborted when the call to
             // ::takeoverCompositorAnimation is made.
             m_runState = RunState::WaitingToSendToCompositor;
         } else {
             abortAnimation();
         }
 
         m_compositorAnimationId = 0;
         m_compositorAnimationGroupId = 0;
         if (m_runState == RunState::WaitingToCancelOnCompositor) {
             postAnimationCleanupAndReset();
             return;
         }
     }
 
-    if (m_runState == RunState::WaitingToSendToCompositor
-        || m_runState == RunState::RunningOnCompositorButNeedsUpdate) {
+    if (m_runState == RunState::RunningOnCompositorButNeedsUpdate
+        || m_runState == RunState::WaitingToCancelOnCompositorButNewScroll) {
+        // Abort the running animation before a new one with an updated
+        // target is added.
+        abortAnimation();
+
+        m_compositorAnimationId = 0;
+        m_compositorAnimationGroupId = 0;
+
+        m_animationCurve->updateTarget(m_timeFunction() - m_startTime,
+            compositorOffsetFromBlinkOffset(m_targetOffset));
+        if (m_runState == RunState::WaitingToCancelOnCompositorButNewScroll)
+            m_animationCurve->setInitialValue(compositorOffsetFromBlinkOffset(currentPosition()));
+        m_runState = RunState::WaitingToSendToCompositor;
+    }
+
+    if (m_runState == RunState::WaitingToSendToCompositor) {
         if (!m_compositorAnimationAttachedToLayerId)
             reattachCompositorPlayerIfNeeded(getScrollableArea()->compositorAnimationTimeline());
 
-        if (m_runState == RunState::RunningOnCompositorButNeedsUpdate) {
-            // Abort the running animation before a new one with an updated
-            // target is added.
-            abortAnimation();
-
-            m_compositorAnimationId = 0;
-            m_compositorAnimationGroupId = 0;
-
-            m_animationCurve->updateTarget(m_timeFunction() - m_startTime,
-                compositorOffsetFromBlinkOffset(m_targetOffset));
-            m_runState = RunState::WaitingToSendToCompositor;
-        }
-
         if (!m_animationCurve) {
             m_animationCurve = adoptPtr(CompositorFactory::current().createScrollOffsetAnimationCurve(
                 compositorOffsetFromBlinkOffset(m_targetOffset),
                 CompositorAnimationCurve::TimingFunctionTypeEaseInOut,
                 m_lastGranularity == ScrollByPixel ?
                     CompositorScrollOffsetAnimationCurve::ScrollDurationInverseDelta :
                     CompositorScrollOffsetAnimationCurve::ScrollDurationConstant));
             m_animationCurve->setInitialValue(compositorOffsetFromBlinkOffset(currentPosition()));
         }
 
@@ skipping 94 matching lines @@
     }
     return true;
 }
 
 DEFINE_TRACE(ScrollAnimator)
 {
     ScrollAnimatorBase::trace(visitor);
 }
 
 } // namespace blink