Implement Custom Elements 'extends' option.

Source/core/dom/CustomElementException.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 46 matching lines @@
         return;
 
     case ContextDestroyedCreatingCallbacks:
         es.throwDOMException(InvalidStateError);
         return;
 
     case ContextDestroyedRegisteringDefinition:
         es.throwDOMException(NotSupportedError);
         return;
 
+    case ExtendsIsInvalidName:
+        es.throwDOMException(InvalidCharacterError, preamble(type) + ": the tag name specified in 'extends' is not a valid tag name.");
+        return;
+
+    case ExtendsIsCustomElementName:
+        es.throwDOMException(InvalidCharacterError, preamble(type) + ": the tag name specified in 'extends' is a custom element name. Use inheritance instead.");
+        return;
+
     case InvalidName:
         es.throwDOMException(InvalidCharacterError, preamble(type) + ": '" + type + "' is not a valid name.");
         return;
 
-    case NotYetImplemented:
-        es.throwDOMException(InvalidStateError);
-        return;
-
-    case PrototypeDoesNotExtendHTMLElementSVGElementNamespace:
-        es.throwDOMException(NamespaceError, preamble(type) + "the prototype does not extend an HTML or SVG element.");
-        return;
-
-    case PrototypeDoesNotExtendHTMLElementSVGElementPrototype:
-        es.throwDOMException(InvalidStateError, preamble(type) + "the prototype does not extend an HTML or SVG element.");
-        return;
-
     case PrototypeInUse:
         es.throwDOMException(NotSupportedError, preamble(type) + "prototype is already in-use as an interface prototype object.");
         return;
 
     case PrototypeNotAnObject:
         es.throwDOMException(InvalidStateError, preamble(type) + "the prototype option is not an object.");
         return;
 
     case TypeAlreadyRegistered:
         es.throwDOMException(InvalidStateError, preamble(type) + "a type with that name is already registered.");
         return;
     }
 
     ASSERT_NOT_REACHED();
 }
 
 } // namespace WebCore