Revert "wrap_jso should wrap JsArray as well, not always call wrap on its contents"

sdk/lib/js/dartium/js_dartium.dart

 // Copyright (c) 2013, 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.
 
 /**
  * Support for interoperating with JavaScript.
  *
  * This library provides access to JavaScript objects from Dart, allowing
  * Dart code to get and set properties, and call methods of JavaScript objects
  * and invoke JavaScript functions. The library takes care of converting
@@ skipping 789 matching lines @@
     }
   }
 
   // Methods required by ListMixin
 
   E operator [](index) {
     if (index is int) {
       _checkIndex(index);
     }
 
-    return super[index];
+    // Lazily create the Dart class that wraps the JS object when the object in
+    // a list if fetched.
+    var wrap_entry = html.wrap_jso(super[index]);
+    super[index] = wrap_entry;
+    return wrap_entry;
   }
 
   void operator []=(index, E value) {
     if (index is int) {
       _checkIndex(index);
     }
     super[index] = value;
   }
 
   int get length native "JsArray_length";
@@ skipping 60 matching lines @@
 
 /**
  * Returns a method that can be called with an arbitrary number (for n less
  * than 11) of arguments without violating Dart type checks.
  */
 Function _wrapAsDebuggerVarArgsFunction(JsFunction jsFunction) =>
     ([a1 = _UNDEFINED, a2 = _UNDEFINED, a3 = _UNDEFINED, a4 = _UNDEFINED,
         a5 = _UNDEFINED, a6 = _UNDEFINED, a7 = _UNDEFINED, a8 = _UNDEFINED,
         a9 = _UNDEFINED, a10 = _UNDEFINED]) => jsFunction._applyDebuggerOnly(
             _stripUndefinedArgs([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]));