remove unused code in fixTemplateElementPrototype

we no longer attempt to fix the prototype of a semantic template element. instead, we "extract" an actual template element.

the invariant with this method is that it is always called with an element with tagName 'template' in the HTML namespace.

R=arv
BUG=

Review URL: https://codereview.appspot.com/52430043

src/TemplateBinding.js

@@ -357,21 +357,10 @@
   }
 
   function fixTemplateElementPrototype(el) {
-    // Note: because we need to treat some semantic elements as template
-    // elements (like tr or td), but don't want to reassign their proto (gecko
-    // doesn't like that), we mixin the properties for those elements.
-    if (el.tagName === 'TEMPLATE') {
-      if (!hasTemplateElement) {
-        if (hasProto)
-          el.__proto__ = HTMLTemplateElement.prototype;
-        else
-          mixin(el, HTMLTemplateElement.prototype);
-      }
-    } else {
+    if (hasProto)
+      el.__proto__ = HTMLTemplateElement.prototype;
+    else
       mixin(el, HTMLTemplateElement.prototype);
-      // FIXME: Won't need this when webkit methods move to the prototype.
-      Object.defineProperty(el, 'content', contentDescriptor);
-    }
   }
 
   function ensureSetModelScheduled(template) {