Make AnimationEffectReadOnly.getComputedTiming() consistent with Web Animations spec

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

Index: third_party/WebKit/Source/core/animation/css/CSSAnimations.cpp
diff --git a/third_party/WebKit/Source/core/animation/css/CSSAnimations.cpp b/third_party/WebKit/Source/core/animation/css/CSSAnimations.cpp
index e357d4bee23f5a46c416002366bea6b4e10e4428..a3b550bd8c96a0cc73c759d5b9a18fb11c745108 100644
--- a/third_party/WebKit/Source/core/animation/css/CSSAnimations.cpp
+++ b/third_party/WebKit/Source/core/animation/css/CSSAnimations.cpp
@@ -539,12 +539,12 @@ void CSSAnimations::calculateTransitionUpdateForProperty(CSSPropertyID id, const
     AnimatableValue* reversingAdjustedStartValue = from.get();
     double reversingShorteningFactor = 1;
     if (interruptedTransition) {
-        const double interruptedTimeFraction = interruptedTransition->animation->effect()->timeFraction();
-        if (!std::isnan(interruptedTimeFraction)) {
+        const double interruptedProgress = interruptedTransition->animation->effect()->progress();
+        if (!std::isnan(interruptedProgress)) {
             // const_cast because we need to take a ref later when passing to startTransition.
             reversingAdjustedStartValue = const_cast<AnimatableValue*>(interruptedTransition->to);
             reversingShorteningFactor = clampTo(
-                (interruptedTimeFraction * interruptedTransition->reversingShorteningFactor) +
+                (interruptedProgress * interruptedTransition->reversingShorteningFactor) +
                 (1 - interruptedTransition->reversingShorteningFactor), 0.0, 1.0);
             timing.iterationDuration *= reversingShorteningFactor;
             if (timing.startDelay < 0) {