Introduce toHTMLFrameElement

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 2226 matching lines @@
     } else if (!parentLayer && renderer()->isBox() && renderBox()->canBeProgramaticallyScrolled()) {
         if (frameView) {
             Element* ownerElement = 0;
             if (renderer()->document())
                 ownerElement = renderer()->document()->ownerElement();
 
             if (ownerElement && ownerElement->renderer()) {
                 HTMLFrameElement* frameElement = 0;
 
                 if (ownerElement->hasTagName(frameTag) || ownerElement->hasTagName(iframeTag))
-                    frameElement = static_cast<HTMLFrameElement*>(ownerElement);

[tkent, 2013/07/17 21:17:45]

We have a bad cast here though it is harmless.

ownerElement can be an HTML*I*FrameElement, and the code casts it to
HTMLFrameElement.
|frameElement| and the first argument of frameElementAndViewPermitScroll()
should be HTMLFrameElementBase* instead of HTMLFrameElement*.

+                    frameElement = toHTMLFrameElement(ownerElement);
 
                 if (frameElementAndViewPermitScroll(frameElement, frameView)) {
                     LayoutRect viewRect = frameView->visibleContentRect();
                     LayoutRect exposeRect = getRectToExpose(viewRect, rect, alignX, alignY);
 
                     int xOffset = roundToInt(exposeRect.x());
                     int yOffset = roundToInt(exposeRect.y());
                     // Adjust offsets if they're outside of the allowable range.
                     xOffset = max(0, min(frameView->contentsWidth(), xOffset));
                     yOffset = max(0, min(frameView->contentsHeight(), yOffset));
@@ skipping 4134 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif