Dart: Makes timing of sending trace events configurable.

examples/dart/traced_application/lib/main.dart

 #!mojo mojo:dart_content_handler
 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This example application illustrates how to use Mojo Tracing from Dart code.
 //
 // To run this app:
 // mojo/devtools/common/mojo_run --trace-startup \
 //   https://core.mojoapps.io/examples/dart/traced_application/lib/main.dart
@@ skipping 11 matching lines @@
 
 class TestUsingTracingApp extends Application {
   TracingHelper _tracing;
   Timer _timer;
 
   TestUsingTracingApp.fromHandle(MojoHandle handle) : super.fromHandle(handle);
 
   void initialize(List<String> args, String url) {
     // This sets up a connection between this application and the Mojo
     // tracing service.
-    _tracing =
-        new TracingHelper.fromApplication(this, "example_traced_application");
+    _tracing = new TracingHelper.fromApplication(
+        this, "example_traced_application", TraceSendTiming.AT_END);
     _tracing.traceInstant("initialized", "traced_application");
 
     // Now we schedule some random work just so we have something to trace.
     _timer = new Timer.periodic(new Duration(seconds: 1), (t) => function1());
 
     onError = (() {
       if (_timer != null) {
         _timer.cancel();
       }
     });
@@ skipping 52 matching lines @@
 }
 
 Future waitForMilliseconds(int milliseconds) {
   return new Future.delayed(new Duration(milliseconds: milliseconds), () {});
 }
 
 main(List args) {
   MojoHandle appHandle = new MojoHandle(args[0]);
   new TestUsingTracingApp.fromHandle(appHandle);
 }