Rework dispatchEvent so it is consistent for isTrusted support.

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 88335cd477fda3e66804440c2f12fb715867b156..41f7df08031f897f2daba0f4b73f3e14869d1bc6 100644
--- a/Source/core/animation/Animation.h
+++ b/Source/core/animation/Animation.h
@@ -114,7 +114,6 @@ public:
     ExecutionContext* executionContext() const override;
     bool hasPendingActivity() const override;
     void stop() override;
-    bool dispatchEvent(PassRefPtrWillBeRawPtr<Event>) override;
 
     double playbackRate() const;
     void setPlaybackRate(double);
@@ -181,6 +180,9 @@ public:
 
     DECLARE_VIRTUAL_TRACE();
 
+protected:
+    bool dispatchEventInternal(PassRefPtrWillBeRawPtr<Event>) override;
+
 private:
     Animation(ExecutionContext*, AnimationTimeline&, AnimationEffect*);