A div can be pan-scrolled beyond its overflow (Windows only)

Source/core/rendering/RenderLayer.cpp

Index: Source/core/rendering/RenderLayer.cpp
diff --git a/Source/core/rendering/RenderLayer.cpp b/Source/core/rendering/RenderLayer.cpp
index 1fa7e9a28017efe08f6930bd7f70768475d379bd..15909fab3cd0dfe2dc242ef00dc3ae5e895f2fd7 100644
--- a/Source/core/rendering/RenderLayer.cpp
+++ b/Source/core/rendering/RenderLayer.cpp
@@ -2154,8 +2154,13 @@ void RenderLayer::panScrollFromPoint(const IntPoint& sourcePoint)
 
 void RenderLayer::scrollByRecursively(const IntSize& delta, ScrollOffsetClamping clamp)
 {
+    scrollBy(delta, clamp, ShouldPropagateScroll);
+}
+
+bool RenderLayer::scrollBy(const IntSize& delta, ScrollOffsetClamping clamp, ScrollPropagation shouldPropagate)
+{
     if (delta.isZero())
-        return;
+        return false;
 
     bool restrictedByLineClamp = false;
     if (renderer()->parent())
@@ -2165,24 +2170,36 @@ void RenderLayer::scrollByRecursively(const IntSize& delta, ScrollOffsetClamping
         IntSize newScrollOffset = adjustedScrollOffset() + delta;
         scrollToOffset(newScrollOffset, clamp);
 
+        if (shouldPropagate == DontPropagateScroll)
+            return true;
+
         // If this layer can't do the scroll we ask the next layer up that can scroll to try
         IntSize remainingScrollOffset = newScrollOffset - adjustedScrollOffset();
+        bool didScroll = true;
         if (!remainingScrollOffset.isZero() && renderer()->parent()) {
             if (RenderLayer* scrollableLayer = enclosingScrollableLayer())
-                scrollableLayer->scrollByRecursively(remainingScrollOffset);
+                didScroll = scrollableLayer->scrollBy(remainingScrollOffset, clamp, shouldPropagate);
 
             Frame* frame = renderer()->frame();
             if (frame)
                 frame->eventHandler()->updateAutoscrollRenderer();
         }
+        return didScroll;
     } else if (renderer()->view()->frameView()) {
         // If we are here, we were called on a renderer that can be programmatically scrolled, but doesn't
         // have an overflow clip. Which means that it is a document node that can be scrolled.
-        renderer()->view()->frameView()->scrollBy(delta);
+        FrameView* view = renderer()->view()->frameView();
+        IntPoint scrollPositionBefore = view->scrollPosition();
+        if (view->isScrollable())
+            view->scrollBy(delta);
+        IntPoint scrollPositionAfter = view->scrollPosition();
+        return scrollPositionBefore != scrollPositionAfter;
 
         // FIXME: If we didn't scroll the whole way, do we want to try looking at the frames ownerElement? 
         // https://bugs.webkit.org/show_bug.cgi?id=28237
     }
+
+    return false;
 }
 
 IntSize RenderLayer::clampScrollOffset(const IntSize& scrollOffset) const