Fix indexed_db strong mode warnings.

sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart

 /**
  * A client-side key-value store with support for indexes.
  *
  * Many browsers support IndexedDB—a web standard for
  * an indexed database.
  * By storing data on the client in an IndexedDB,
  * a web app gets some advantages, such as faster performance and persistence.
  * To find out which browsers support IndexedDB,
  * refer to [Can I Use?](http://caniuse.com/#feat=indexeddb)
  *
@@ skipping 535 matching lines @@
         request.onBlocked.listen(onBlocked);
       }
       return _completeRequest(request);
     } catch (e, stacktrace) {
       return new Future.error(e, stacktrace);
     }
   }
 
   @DomName('IDBFactory.deleteDatabase')
   Future<IdbFactory> deleteDatabase(String name,
-      {void onBlocked(Event)}) {
+      {void onBlocked(Event e)}) {
     try {
       var request = _deleteDatabase(name);
 
       if (onBlocked != null) {
         request.onBlocked.listen(onBlocked);
       }
-      var completer = new Completer.sync();
+      var completer = new Completer<IdbFactory>.sync();
       request.onSuccess.listen((e) {
         completer.complete(this);
       });
       request.onError.listen(completer.completeError);
       return completer.future;
     } catch (e, stacktrace) {
       return new Future.error(e, stacktrace);
     }
   }
 
@@ skipping 49 matching lines @@
   @Creates('DomStringList')
   Request _webkitGetDatabaseNames() native;
 
 }
 
 
 /**
  * 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.sync();
+Future/*<T>*/ _completeRequest/*<T>*/(Request request) {
+  var completer = new Completer/*<T>*/.sync();
   // 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);
+    completer.complete(request.result as dynamic/*=T*/);
   });
   request.onError.listen(completer.completeError);
   return completer.future;
 }
 // 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.
 
 
 @DomName('IDBIndex')
@@ skipping 519 matching lines @@
   @DocsEditable()
   @Returns('Request')
   @Creates('Request')
   @_annotation_Creates_IDBKey
   Request _put_2(value) native;
 
 
   /**
    * Helper for iterating over cursors in a request.
    */
-  static Stream<Cursor> _cursorStreamFromResult(Request request,
+  static Stream/*<T>*/ _cursorStreamFromResult/*<T extends Cursor>*/(Request request,
       bool autoAdvance) {
     // TODO: need to guarantee that the controller provides the values
     // immediately as waiting until the next tick will cause the transaction to
     // close.
-    var controller = new StreamController(sync: true);
+    var controller = new StreamController/*<T>*/(sync: true);
 
     //TODO: Report stacktrace once issue 4061 is resolved.
     request.onError.listen(controller.addError);
 
     request.onSuccess.listen((e) {
-      Cursor cursor = request.result;
+      var cursor = request.result as dynamic /*=T*/;
       if (cursor == null) {
         controller.close();
       } else {
         controller.add(cursor);
         if (autoAdvance == true && controller.hasListener) {
           cursor.next();
         }
       }
     });
     return controller.stream;
@@ skipping 265 matching lines @@
   @Creates('int|String|Null')
   @Returns('int|String|Null')
   final int newVersion;
 
   @DomName('IDBVersionChangeEvent.oldVersion')
   @DocsEditable()
   @Creates('int|String|Null')
   @Returns('int|String|Null')
   final int oldVersion;
 }