Rework dispatchEvent so it is consistent for isTrusted support.

Source/core/animation/Animation.cpp

Index: Source/core/animation/Animation.cpp
diff --git a/Source/core/animation/Animation.cpp b/Source/core/animation/Animation.cpp
index 3a9c5c7aa20a4554ae85d85bfef5ce4d75338826..272870789019e657c6ee3c97914f2af3a18c17cc 100644
--- a/Source/core/animation/Animation.cpp
+++ b/Source/core/animation/Animation.cpp
@@ -643,11 +643,11 @@ void Animation::stop()
     m_pendingFinishedEvent = nullptr;
 }
 
-bool Animation::dispatchEvent(PassRefPtrWillBeRawPtr<Event> event)
+bool Animation::dispatchEventInternal(PassRefPtrWillBeRawPtr<Event> event)
 {
     if (m_pendingFinishedEvent == event)
         m_pendingFinishedEvent = nullptr;
-    return EventTargetWithInlineData::dispatchEvent(event);
+    return EventTargetWithInlineData::dispatchEventInternal(event);
 }
 
 double Animation::playbackRate() const