Fix indexed_db strong mode warnings.

sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart

Index: sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart
diff --git a/sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart b/sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart
index f969eb3f36ec3a65ba1c6d087c8ff2e941076aa0..a69b9bcb6c8932d93ab7dedf85fba90bedac178e 100644
--- a/sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart
+++ b/sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart
@@ -553,14 +553,14 @@ class IdbFactory extends Interceptor {
 
   @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);
       });
@@ -630,12 +630,12 @@ class IdbFactory extends Interceptor {
  * 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;
@@ -1175,18 +1175,18 @@ class ObjectStore extends Interceptor {
   /**
    * 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 {