Pull "$instanceOf" methods off of the native object. No change in behavior.

compiler/lib/implementation/string.js

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/**
- * Extend the String prototype with members expected in dart.
- */
-
-String.$instanceOf = function(obj) {
-  return typeof obj == 'string' || obj instanceof String;
-};
-
 function native_StringImplementation__indexOperator(index) {
   return this[index];
 }
 
 function native_StringImplementation__charCodeAt(index) {
   return this.charCodeAt(index);
 }
 
 function native_StringImplementation_get$length() {
   return this.length;
@@ skipping 28 matching lines @@
 function native_StringImplementation__substringUnchecked(startIndex, endIndex) {
   return this.substring(startIndex, endIndex);
 }
 
 function native_StringImplementation_trim() {
   if (this.trim) return this.trim();
   return this.replace(new RegExp("^[\s]+|[\s]+$", "g"), "");
 }
 
 function native_StringImplementation__replace(from, to) {
-  if (String.$instanceOf(from)) {
+  if ($isString(from)) {
     return this.replace(from, to);
   } else {
     return this.replace($DartRegExpToJSRegExp(from), to);
   }
 }
 
 function native_StringImplementation__replaceAll(from, to) {
-  if (String.$instanceOf(from)) {
+  if ($isString(from)) {
     var regexp = new RegExp(
         from.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&"), 'g');
     return this.replace(regexp, to);
   } else {
     var regexp = $DartRegExpToJSRegExp(from);
     return this.replace(regexp, to);
   }
 }
 
 function native_StringImplementation__split(pattern) {
-  if (String.$instanceOf(pattern)) {
+  if ($isString(pattern)) {
     return this.split(pattern);
   } else {
     return this.split($DartRegExpToJSRegExp(pattern));
   }
 }
 
 function native_StringImplementation_toLowerCase() {
   return this.toLowerCase();
 }
 
@@ skipping 41 matching lines @@
     }
     array = tmp;
   }
   return String.fromCharCode.apply(this, array);
 }
 
 // Deprecated old name of new String.fromValues(..).
 function native_StringBase_createFromCharCodes(array) {
   return native_StringImplementation__newFromValues(array);
 }