Clear started transitions overwritten by duration 0 transitions on the same property

third_party/WebKit/Source/core/animation/css/CSSAnimations.cpp

 /*
  * Copyright (C) 2013 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 659 matching lines @@
   // No smooth interpolation exists between these values so don't start a
   // transition.
   if (!transitionType) {
     return;
   }
 
   // If we have multiple transitions on the same property, we will use the
   // last one since we iterate over them in order.
 
   Timing timing = transitionData.convertToTiming(transitionIndex);
-  if (timing.startDelay + timing.iterationDuration <= 0)
+  if (timing.startDelay + timing.iterationDuration <= 0) {
+    // We may have started a transition in a prior CSSTransitionData update,
+    // this CSSTransitionData update needs to override them.
+    // TODO(alancutter): Just iterate over the CSSTransitionDatas in reverse and
+    // skip any properties that have already been visited so we don't need to
+    // "undo" work like this.
+    update.unstartTransition(id);
     return;
+  }
 
   AnimatableValue* reversingAdjustedStartValue = from.get();
   double reversingShorteningFactor = 1;
   if (interruptedTransition) {
     const double interruptedProgress =
         interruptedTransition->animation->effect()->progress();
     if (!std::isnan(interruptedProgress)) {
       reversingAdjustedStartValue = interruptedTransition->to.get();
       reversingShorteningFactor =
           clampTo((interruptedProgress *
@@ skipping 419 matching lines @@
              isCustomPropertyHandle);
 }
 
 DEFINE_TRACE(CSSAnimations) {
   visitor->trace(m_transitions);
   visitor->trace(m_pendingUpdate);
   visitor->trace(m_runningAnimations);
 }
 
 }  // namespace blink