Ignore should-scroll-on-main-thread if main frame is not scrollable

Source/core/page/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 651 matching lines @@
         RenderObject* rootRenderer = documentElement ? documentElement->renderer() : 0;
         Node* body = document->body();
         if (body && body->renderer()) {
             if (body->hasTagName(framesetTag)) {
                 vMode = ScrollbarAlwaysOff;
                 hMode = ScrollbarAlwaysOff;
             } else if (body->hasTagName(bodyTag)) {
                 // It's sufficient to just check the X overflow,
                 // since it's illegal to have visible in only one direction.
                 RenderObject* o = rootRenderer->style()->overflowX() == OVISIBLE && isHTMLHtmlElement(document->documentElement()) ? body->renderer() : rootRenderer;
-                applyOverflowToViewport(o, hMode, vMode);
+                if (o->style())
+                    applyOverflowToViewport(o, hMode, vMode);
             }
         } else if (rootRenderer)
             applyOverflowToViewport(rootRenderer, hMode, vMode);
     }
 }
 
 void FrameView::updateCompositingLayersAfterStyleChange()
 {
     TRACE_EVENT0("webkit", "FrameView::updateCompositingLayersAfterStyleChange");
     RenderView* renderView = this->renderView();
@@ skipping 2697 matching lines @@
         return frame().document()->existingAXObjectCache();
     return 0;
 }
 
 bool FrameView::isMainFrame() const
 {
     return m_frame->page() && m_frame->page()->mainFrame() == m_frame;
 }
 
 } // namespace WebCore