Workaround to re-enable test

This is a workaround for:
   https://github.com/dart-lang/sdk/issues/25246

packages/flutter/lib/src/scheduler/scheduler.dart

@@ -95,12 +95,11 @@ abstract class Scheduler extends BindingBase {
 
   SchedulingStrategy schedulingStrategy = new DefaultSchedulingStrategy();
 
-  final PriorityQueue _taskQueue = new HeapPriorityQueue<_TaskEntry>(
-    (_TaskEntry e1, _TaskEntry e2) {
-      // Note that we inverse the priority.
-      return -e1.priority.compareTo(e2.priority);
-    }
-  );
+  static int _taskSorter (_TaskEntry e1, _TaskEntry e2) {
+    // Note that we inverse the priority.
+    return -e1.priority.compareTo(e2.priority);
+  }
+  final PriorityQueue _taskQueue = new HeapPriorityQueue<_TaskEntry>(_taskSorter);
 
   /// Whether this scheduler already requested to be called from the event loop.
   bool _hasRequestedAnEventLoopCallback = false;