Fixing Location.origin to work on non-WebKit browsers.

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

+// 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.
+
+part of $LIBRARYNAME;
+
+@DocsEditable
+$(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
+$!MEMBERS
+
+$if DART2JS
+  @DomName('Location.origin')
+  String get origin {
+    if (JS('bool', '("origin" in #)', this)) {
+      return JS('String', '#.origin', this);
+    }
+    return '${this.protocol}//${this.host}';
+  }
+$endif
+}