fixes #175, fixed arrays

tool/input_sdk/private/js_array.dart

 // Copyright (c) 2012, 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.
 
 part of _interceptors;
 
 /**
  * The interceptor class for [List]. The compiler recognizes this
  * class as an interceptor, and changes references to [:this:] to
  * actually use the receiver of the method, which is generated as an extra
@@ skipping 67 matching lines @@
     return JS('JSFixedArray', '#', list);
   }
 
   checkMutable(reason) {
     if (this is !JSMutableArray) {
       throw new UnsupportedError(reason);
     }
   }
 
   checkGrowable(reason) {
-    if (this is !JSExtendableArray) {
+    if (JS('bool', r'#.fixed$length', this)) {
       throw new UnsupportedError(reason);
     }
   }
 
   void add(E value) {
     checkGrowable('add');
     JS('void', r'#.push(#)', this, value);
   }
 
   E removeAt(int index) {
@@ skipping 282 matching lines @@
 }
 
 /**
  * Dummy subclasses that allow the backend to track more precise
  * information about arrays through their type. The CPA type inference
  * relies on the fact that these classes do not override [] nor []=.
  */
 class JSMutableArray<E> extends JSArray<E> implements JSMutableIndexable {}
 class JSFixedArray<E> extends JSMutableArray<E> {}
 class JSExtendableArray<E> extends JSMutableArray<E> {}