Disable clipping on root scroller's ancestors.

third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp

Index: third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp
diff --git a/third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp b/third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp
index b23bf7cfd2002b6d4170398fc7fb00fdb6675afa..417bd5278b78466748afcf0f0967c44951469440 100644
--- a/third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp
+++ b/third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp
@@ -94,10 +94,10 @@ void TopDocumentRootScrollerController::updateGlobalRootScroller()
 
 void TopDocumentRootScrollerController::didUpdateCompositing()
 {
-    FrameHost* frameHost = m_document->frameHost();
+    RootScrollerController::didUpdateCompositing();
 
     // Let the compositor-side counterpart know about this change.
-    if (frameHost)
+    if (FrameHost* frameHost = m_document->frameHost())
         frameHost->chromeClient().registerViewportLayers();
 }
 
@@ -148,4 +148,9 @@ GraphicsLayer* TopDocumentRootScrollerController::rootScrollerLayer()
     return graphicsLayer;
 }
 
+Element* TopDocumentRootScrollerController::globalRootScroller() const
+{
+    return m_globalRootScroller.get();
+}
+
 } // namespace blink