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

Source/core/animation/Animation.h

Index: Source/core/animation/Animation.h
diff --git a/Source/core/animation/Animation.h b/Source/core/animation/Animation.h
index 3401708ded92e371e34462b5937894b8e0f063f8..ea772ae55422e79b6ad7d1aae6c579dfd8a31b56 100644
--- a/Source/core/animation/Animation.h
+++ b/Source/core/animation/Animation.h
@@ -50,6 +50,10 @@ public:
         return m_compositableValues.get();
     }
 
+    // This is used by CSS to make sure events are fired on animations with
+    // zero start delay.
+    void forceSampleBeforeStartTime() { updateInheritedTime(startTime() - 1); }
+
 protected:
     virtual void applyEffects(bool previouslyInEffect);
     virtual void clearEffects();