Move the Widget hierarchy to the Oilpan heap.

Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.cpp b/Source/core/page/scrolling/ScrollingCoordinator.cpp
index 9065ee3fd29c5bec78e7d5bd0d85ad734b35737c..98b6e9c02b8f215cd6ed7e9d32f52c7dbfe1b6c4 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -241,7 +241,7 @@ static PassOwnPtr<WebScrollbarLayer> createScrollbarLayer(Scrollbar* scrollbar)
     blink::WebScrollbarThemePainter painter(theme, scrollbar);
     OwnPtr<blink::WebScrollbarThemeGeometry> geometry(blink::WebScrollbarThemeGeometryNative::create(theme));
 
-    OwnPtr<WebScrollbarLayer> scrollbarLayer = adoptPtr(blink::Platform::current()->compositorSupport()->createScrollbarLayer(new blink::WebScrollbarImpl(scrollbar), painter, geometry.leakPtr()));
+    OwnPtr<WebScrollbarLayer> scrollbarLayer = adoptPtr(blink::Platform::current()->compositorSupport()->createScrollbarLayer(WebScrollbarImpl::create(scrollbar), painter, geometry.leakPtr()));
     GraphicsLayer::registerContentsLayer(scrollbarLayer->layer());
     return scrollbarLayer.release();
 }
@@ -724,8 +724,8 @@ Region ScrollingCoordinator::computeShouldHandleScrollGestureOnMainThreadRegion(
         }
     }
 
-    if (const HashSet<RefPtr<Widget> >* children = frameView->children()) {
-        for (HashSet<RefPtr<Widget> >::const_iterator it = children->begin(), end = children->end(); it != end; ++it) {
+    if (const WillBeHeapHashSet<RefPtrWillBeMember<Widget> >* children = frameView->children()) {
+        for (WillBeHeapHashSet<RefPtrWillBeMember<Widget> >::const_iterator it = children->begin(), end = children->end(); it != end; ++it) {
             if (!(*it)->isPluginView())
                 continue;