Viewport apply scroll should be on the document element not scrollingElement.

third_party/WebKit/Source/core/input/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 615 matching lines @@
         controller->stopAutoscroll();
 }
 
 ScrollResult EventHandler::scrollBox(LayoutBox* box,
     ScrollGranularity granularity, const FloatSize& delta,
     const FloatPoint& position, const FloatSize& velocity,
     bool* wasRootScroller)
 {
     ASSERT(box);
     Node* node = box->node();
-    Document* document = m_frame->document();
-    Element* scrollingElement = document->scrollingElement();
-
-    bool isRootFrame = !document->ownerElement();
-
-    // TODO(bokan): If the ViewportScrollCallback is installed on the body, we
-    // can still hit the HTML element for scrolling in which case it'll bubble
-    // up to the document node and try to scroll the LayoutView directly. Make
-    // sure we never scroll the LayoutView like this by manually resetting the
-    // scroll to happen on the scrolling element. This can also happen in
-    // QuirksMode when the body is scrollable and scrollingElement == nullptr.
-    if (node && node->isDocumentNode() && isRootFrame) {
-        node = scrollingElement
-            ? scrollingElement
-            : document->documentElement();
-    }
 
     // If there's no ApplyScroll callback on the element, scroll as usuall in
     // the non-scroll-customization case.
     if (!node || !node->isElementNode() || !toElement(node)->getApplyScroll()) {
-        ASSERT(!isRootFrame
-            || node != scrollingElement
-            || (!scrollingElement && node != document->documentElement()));
         *wasRootScroller = false;
         return box->scroll(granularity, delta);
     }
 
-    ASSERT(isRootFrame);
+    // Viewport actions should only happen when scrolling an element in the
+    // main frame.
+    ASSERT(m_frame->isMainFrame());
 
     // If there is an ApplyScroll callback, its because we placed one on the
     // root scroller to control top controls and overscroll. Invoke a scroll
     // using parts of the scroll customization framework on just this element.
     computeScrollChainForSingleNode(*node, m_currentScrollChain);
 
     OwnPtr<ScrollStateData> scrollStateData = adoptPtr(new ScrollStateData());
     scrollStateData->delta_x = delta.width();
     scrollStateData->delta_y = delta.height();
     scrollStateData->position_x = position.x();
@@ skipping 3475 matching lines @@
 PlatformEvent::Modifiers EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return static_cast<PlatformEvent::Modifiers>(PlatformEvent::CtrlKey | PlatformEvent::AltKey);
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink