Support JS$ prefix for dart and fix bug where _operator_getter and the [] operator were used incons…

sdk/lib/web_gl/dartium/web_gl_dartium.dart

 /**
  * 3D programming in the browser.
  */
 library dart.dom.web_gl;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_internal';
 import 'dart:html';
 import 'dart:html_common';
@@ skipping 806 matching lines @@
 class ContextEvent extends Event {
   // To suppress missing implicit constructor warnings.
   factory ContextEvent._() { throw new UnsupportedError("Not supported"); }
 
 
   @Deprecated("Internal Use Only")
   static ContextEvent internalCreateContextEvent() {
     return new ContextEvent._internalWrap();
   }
 
-  factory ContextEvent._internalWrap() {
-    return new ContextEvent.internal_();
-  }
+  external factory ContextEvent._internalWrap();
 
   @Deprecated("Internal Use Only")
   ContextEvent.internal_() : super.internal_();
 
 
   @DomName('WebGLContextEvent.statusMessage')
   @DocsEditable()
   String get statusMessage => _blink.BlinkWebGLContextEvent.instance.statusMessage_Getter_(unwrap_jso(this));
   
 }
@@ skipping 2906 matching lines @@
 
 
 @DocsEditable()
 @DomName('WebGLRenderingContextBase')
 @Experimental() // untriaged
 class _WebGLRenderingContextBase extends DartHtmlDomObject {
   // To suppress missing implicit constructor warnings.
   factory _WebGLRenderingContextBase._() { throw new UnsupportedError("Not supported"); }
 
 }