Introduce toHTMLFrameElement

Source/core/rendering/RenderLayer.cpp

Index: Source/core/rendering/RenderLayer.cpp
diff --git a/Source/core/rendering/RenderLayer.cpp b/Source/core/rendering/RenderLayer.cpp
index 07820f1163a2a1b1737362f65d4f2fdbfe656888..01aa012342092e7de1097d16f7bc9de06c20e17c 100644
--- a/Source/core/rendering/RenderLayer.cpp
+++ b/Source/core/rendering/RenderLayer.cpp
@@ -2244,7 +2244,7 @@ void RenderLayer::scrollRectToVisible(const LayoutRect& rect, const ScrollAlignm
                 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();