Use new is*Element() helper functions further more in HTML code

Source/core/html/HTMLMapElement.cpp

Index: Source/core/html/HTMLMapElement.cpp
diff --git a/Source/core/html/HTMLMapElement.cpp b/Source/core/html/HTMLMapElement.cpp
index 02c70e977a7fe086c09bb0e45555cba40f0364e2..88938ef4e3545932c1fe1de037b019ec9ec3e60d 100644
--- a/Source/core/html/HTMLMapElement.cpp
+++ b/Source/core/html/HTMLMapElement.cpp
@@ -74,15 +74,14 @@ HTMLImageElement* HTMLMapElement::imageElement()
 {
     RefPtr<HTMLCollection> images = document().images();
     for (unsigned i = 0; Element* curr = images->item(i); i++) {
-        if (!curr->hasTagName(imgTag))
-            continue;
+        ASSERT(isHTMLImageElement(curr));

[adamk, 2014/03/13 20:20:36]

I take it this is just asserting that Document::images() always returns image
elements...would be nice if we could represent that somehow in the C++ type even
if we can't in the DOM API. But that's for another time.

 
         // The HTMLImageElement's useMap() value includes the '#' symbol at the beginning,
         // which has to be stripped off.
-        HTMLImageElement* imageElement = toHTMLImageElement(curr);
-        String useMapName = imageElement->getAttribute(usemapAttr).string().substring(1);
+        HTMLImageElement& imageElement = toHTMLImageElement(*curr);
+        String useMapName = imageElement.getAttribute(usemapAttr).string().substring(1);
         if (equalIgnoringCase(useMapName, m_name))
-            return imageElement;
+            return &imageElement;
     }
 
     return 0;