Update Custom Elements API to new names.

LayoutTests/fast/dom/custom/resources/document-register-fuzz.js

 
 function setupObjectHooks(hooks)
 {
     // Wrapper for these object should be materialized before setting hooks.
     console.log;
     document.register;
     HTMLSpanElement.prototype;
 
     Object.defineProperty(Object.prototype, "prototype", {
         get: function() { return hooks.prototypeGet(); },
@@ skipping 11 matching lines @@
 function exerciseDocumentRegister()
 {
     register('x-a', {});
     register('x-b', {prototype: Object.create(HTMLElement.prototype)});
 }
 
 function register(name, options)
 {
     var myConstructor = null;
     try {
-        myConstructor = document.register(name, options);
+        myConstructor = document.registerElement(name, options);
     } catch (e) { }
 
     try {
         if (!myConstructor) {
             debug("Constructor object isn't created.");
             return;
         }
 
         if (myConstructor.prototype != options.prototype) {
             console.log("FAIL: bad prototype");
             return;
          }
 
         var element = new myConstructor();
         if (!element)
             return;
         if (element.constructor != myConstructor) {
             console.log("FAIL: bad constructor");
             return;
          }
     } catch (e) { console.log(e); }
 }