Web Animations: Fix CSS events to handle animations with very short durations

Source/core/animation/css/CSSAnimations.cpp

Index: Source/core/animation/css/CSSAnimations.cpp
diff --git a/Source/core/animation/css/CSSAnimations.cpp b/Source/core/animation/css/CSSAnimations.cpp
index b3358ea2f2663d0ff71422e4fbc9c34b39e94fe6..5bbde26e9122da361a3ba401c5e5ec07bceb94a1 100644
--- a/Source/core/animation/css/CSSAnimations.cpp
+++ b/Source/core/animation/css/CSSAnimations.cpp
@@ -191,8 +191,11 @@ void CSSAnimations::update(Element* element, const RenderStyle* style)
                 OwnPtr<CSSAnimations::EventDelegate> eventDelegate = adoptPtr(new EventDelegate(element, animationName));
                 ASSERT(!isNull(element->document()->timeline()->currentTime()));
                 // FIXME: crbug.com/268791 - Keyframes are already normalized, perhaps there should be a flag on KeyframeAnimationEffect to skip normalization.
-                m_animations.set(animationName.impl(), element->document()->timeline()->play(
-                    Animation::create(element, KeyframeAnimationEffect::create(keyframes), timing, eventDelegate.release()).get()).get());
+                RefPtr<Animation> animation = Animation::create(element, KeyframeAnimationEffect::create(keyframes), timing, eventDelegate.release());
+                // If the start delay is zero, force a sample to make sure events fire.
+                if (!timing.startDelay)
+                    animation->forceSampleBeforeStartTime();
+                m_animations.set(animationName.impl(), element->document()->timeline()->play(animation.get()).get());
             }
         }
     }
@@ -215,7 +218,7 @@ void CSSAnimations::EventDelegate::maybeDispatch(Document::ListenerType listener
         m_target->document()->timeline()->addEventToDispatch(m_target, AnimationEvent::create(eventName, m_name, elapsedTime));
 }
 
-void CSSAnimations::EventDelegate::onEventCondition(bool wasInPlay, bool isInPlay, double previousIteration, double currentIteration)
+void CSSAnimations::EventDelegate::onEventCondition(bool wasInPlay, bool isInPlay, bool wasCurrent, bool isCurrent, double previousIteration, double currentIteration)
 {
     // Events for a single document are queued and dispatched as a group at
     // the end of DocumentTimeline::serviceAnimations.
@@ -223,18 +226,18 @@ void CSSAnimations::EventDelegate::onEventCondition(bool wasInPlay, bool isInPla
     // trigger a timer to dispatch when control is released.
     // FIXME: Receive TimedItem as param in order to produce correct elapsed time value.
     double elapsedTime = 0;
-    if (!wasInPlay && isInPlay) {
-        maybeDispatch(Document::ANIMATIONSTART_LISTENER, eventNames().webkitAnimationStartEvent, elapsedTime);
-        return;
-    }
     if (wasInPlay && isInPlay && currentIteration != previousIteration) {
         maybeDispatch(Document::ANIMATIONITERATION_LISTENER, eventNames().webkitAnimationIterationEvent, elapsedTime);
         return;
     }
-    if (wasInPlay && !isInPlay) {
+    bool wasBefore = !wasInPlay && wasCurrent;
+    bool isBefore = !isInPlay && isCurrent;
+    if (wasBefore && !isBefore)
+        maybeDispatch(Document::ANIMATIONSTART_LISTENER, eventNames().webkitAnimationStartEvent, elapsedTime);
+    bool wasAfter = !wasInPlay && !wasCurrent;
+    bool isAfter = !isInPlay && !isCurrent;
+    if (!wasAfter && isAfter)
         maybeDispatch(Document::ANIMATIONEND_LISTENER, eventNames().webkitAnimationEndEvent, elapsedTime);
-        return;
-    }
 }
 
 } // namespace WebCore