Fixing Indexed DB supported check.

tools/dom/templates/html/impl/impl_IDBFactory.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;
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   /**
    * Checks to see if Indexed DB is supported on the current platform.
    */
@@ skipping 62 matching lines @@
     } catch (e, stacktrace) {
       return new Future.immediateError(e, stacktrace);
     }
   }
 
   /**
    * Checks to see if getDatabaseNames is supported by the current platform.
    */
   bool get supportsDatabaseNames {
 $if DART2JS
-    return JS('bool', '!!(#.getDatabaseNames || #.webkitGetDatabaseNames)',
-        this, this);
+    return supported && JS('bool',
+        '!!(#.getDatabaseNames || #.webkitGetDatabaseNames)', this, this);
 $else
     return true;
 $endif
   }
 
 $!MEMBERS
 }
 
 
 /**
  * Ties a request to a completer, so the completer is completed when it succeeds
  * and errors out when the request errors.
  */
 Future _completeRequest(Request request) {
   var completer = new Completer();
   // TODO: make sure that completer.complete is synchronous as transactions
   // may be committed if the result is not processed immediately.
   request.onSuccess.listen((e) {
     completer.complete(request.result);
   });
   request.onError.listen((e) {
     completer.completeError(e);
   });
   return completer.future;
 }