Introduce toHTMLIFrameElement

Source/core/rendering/RenderEmbeddedObject.cpp

Index: Source/core/rendering/RenderEmbeddedObject.cpp
diff --git a/Source/core/rendering/RenderEmbeddedObject.cpp b/Source/core/rendering/RenderEmbeddedObject.cpp
index f338333b20e13668f4c812ce08eb406baf624561..d70f0617129aac282e40012b439d80048acc06a8 100644
--- a/Source/core/rendering/RenderEmbeddedObject.cpp
+++ b/Source/core/rendering/RenderEmbeddedObject.cpp
@@ -268,7 +268,7 @@ void RenderEmbeddedObject::viewCleared()
         int marginWidth = -1;
         int marginHeight = -1;
         if (node()->hasTagName(iframeTag)) {
-            HTMLIFrameElement* frame = static_cast<HTMLIFrameElement*>(node());
+            HTMLIFrameElement* frame = toHTMLIFrameElement(node());
             marginWidth = frame->marginWidth();
             marginHeight = frame->marginHeight();
         }