Adding supported checks and flags to FormData

tools/dom/templates/html/impl/impl_XMLHttpRequest.darttemplate

 // 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 $LIBRARYNAME;
 
 /**
  * A utility for retrieving data from a URL.
  *
  * HttpRequest can be used to obtain data from http, ftp, and file
@@ skipping 104 matching lines @@
 
     if (sendData != null) {
       xhr.send(sendData);
     } else {
       xhr.send();
     }
 
     return completer.future;
   }
 
+  /**
+   * Checks to see if the Progress event is supported on the current platform.
+   */
+  static bool get supportsProgressEvent {
+$if DART2JS
+    var xhr = new HttpRequest();
+    return JS('bool', '"onprogress" in #', xhr);
+$else
+    return true;
+$endif
+  }
+
+  /**
+   * Checks to see if the LoadEnd event is supported on the current platform.
+   */
+  static bool get supportsLoadEndEvent {

[Emily Fortuna, 2013/02/14 23:51:41]

can these be added to the table of js_support_checks instead?

+$if DART2JS
+    var xhr = new HttpRequest();
+    return JS('bool', '"onloadend" in #', xhr);
+$else
+    return true;
+$endif
+  }
+
 $!MEMBERS
 }