Implement CSSOM Smooth Scroll API

Source/core/frame/LocalDOMWindow.h

Index: Source/core/frame/LocalDOMWindow.h
diff --git a/Source/core/frame/LocalDOMWindow.h b/Source/core/frame/LocalDOMWindow.h
index d8c2288dc99ab25d6963eb754c22c9b0267db401..e0907921627de4e455856e3bf3560b102b794b74 100644
--- a/Source/core/frame/LocalDOMWindow.h
+++ b/Source/core/frame/LocalDOMWindow.h
@@ -34,6 +34,7 @@
 #include "platform/LifecycleContext.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
+#include "platform/scroll/ScrollableArea.h"
 
 #include "wtf/Forward.h"
 
@@ -232,9 +233,9 @@ enum PageshowEventPersistence {
         void postMessageTimerFired(PassOwnPtr<PostMessageTimer>);
         void dispatchMessageEventWithOriginCheck(SecurityOrigin* intendedTargetOrigin, PassRefPtrWillBeRawPtr<Event>, PassRefPtrWillBeRawPtr<ScriptCallStack>);
 
-        void scrollBy(int x, int y) const;
+        void scrollBy(int x, int y, ScrollBehavior = ScrollBehaviorAuto) const;
         void scrollBy(int x, int y, const Dictionary& scrollOptions, ExceptionState&) const;
-        void scrollTo(int x, int y) const;
+        void scrollTo(int x, int y, ScrollBehavior = ScrollBehaviorAuto) const;
         void scrollTo(int x, int y, const Dictionary& scrollOptions, ExceptionState&) const;
         void scroll(int x, int y) const { scrollTo(x, y); }
         void scroll(int x, int y, const Dictionary& scrollOptions, ExceptionState& exceptionState) const { scrollTo(x, y, scrollOptions, exceptionState); }