fixes #150, broken code in js_number.dart

test/generated_sdk/lib/_internal/compiler/js_lib/js_number.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 super interceptor class for [JSInt] and [JSDouble]. The compiler
  * recognizes this class as an interceptor, and changes references to
  * [:this:] to actually use the receiver of the method, which is
@@ skipping 148 matching lines @@
   static String _handleIEtoString(String result) {
     // Result is probably IE's untraditional format for large numbers,
     // e.g., "8.0000000000008(e+15)" for 0x8000000000000800.toString(16).
     var match = JS('List|Null',
                    r'/^([\da-z]+)(?:\.([\da-z]+))?\(e\+(\d+)\)$/.exec(#)',
                    result);
     if (match == null) {
       // Then we don't know how to handle it at all.
       throw new UnsupportedError("Unexpected toString result: $result");
     }
-    String result = JS('String', '#', match[1]);
+    result = JS('String', '#', match[1]);
     int exponent = JS("int", "+#", match[3]);
     if (match[2] != null) {
       result = JS('String', '# + #', result, match[2]);
       exponent -= JS('int', '#.length', match[2]);
     }
     return result + "0" * exponent;
   }
 
   // Note: if you change this, also change the function [S].
   String toString() {
@@ skipping 233 matching lines @@
 }
 
 class JSDouble extends JSNumber implements double {
   const JSDouble();
   Type get runtimeType => double;
 }
 
 class JSPositiveInt extends JSInt {}
 class JSUInt32 extends JSPositiveInt {}
 class JSUInt31 extends JSUInt32 {}