Add type casts for KeyframeEffectReadOnly

third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.h

Index: third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.h
diff --git a/third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.h b/third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.h
index 3b90e94370d516317070154217cfd2516877da03..44e5ac083c97784dbeaba23214c450905f85f654 100644
--- a/third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.h
+++ b/third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.h
@@ -46,6 +46,8 @@ class CORE_EXPORT KeyframeEffectReadOnly : public AnimationEffectReadOnly {
 
   ~KeyframeEffectReadOnly() override {}
 
+  bool isKeyframeEffectReadOnly() const override { return true; }
+
   Priority getPriority() const { return m_priority; }
   void downgradeToNormal() { m_priority = DefaultPriority; }
 
@@ -65,6 +67,14 @@ class CORE_EXPORT KeyframeEffectReadOnly : public AnimationEffectReadOnly {
   Priority m_priority;
 };
 
+// TODO(suzyh): Replace calls to toKeyframeEffect with toKeyframeEffectReadOnly
+// where possible
+DEFINE_TYPE_CASTS(KeyframeEffectReadOnly,
+                  AnimationEffectReadOnly,
+                  animationNode,
+                  animationNode->isKeyframeEffectReadOnly(),
+                  animationNode.isKeyframeEffectReadOnly());
+
 }  // namespace blink
 
 #endif  // KeyframeEffectReadOnly_h