Hook up window.scrollTo and friends.

Source/core/rendering/RenderLayerScrollableArea.h

Index: Source/core/rendering/RenderLayerScrollableArea.h
diff --git a/Source/core/rendering/RenderLayerScrollableArea.h b/Source/core/rendering/RenderLayerScrollableArea.h
index c433da7ce54e781e05f18a9be730ea16a58aaa96..680bc21c9f266202ee8ce16dae646df026cf2fc5 100644
--- a/Source/core/rendering/RenderLayerScrollableArea.h
+++ b/Source/core/rendering/RenderLayerScrollableArea.h
@@ -136,6 +136,11 @@ public:
         scrollToOffset(DoubleSize(scrollXOffset(), y), clamp, scrollBehavior);
     }
 
+    virtual void setScrollPosition(const DoublePoint& position, ScrollBehavior scrollBehavior = ScrollBehaviorInstant) override
+    {
+        scrollToOffset(toDoubleSize(position), ScrollOffsetClamped, scrollBehavior);
+    }
+
     void updateAfterLayout();
     void updateAfterStyleChange(const RenderStyle*);
     void updateAfterOverflowRecalc();