Special-case Timeline.{start,finish}Sync for Fuchsia

runtime/lib/timeline.dart

 // Copyright (c) 2015, 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.
 
 @patch
 bool _isDartStreamEnabled() native "Timeline_isDartStreamEnabled";
 
 @patch
 int _getTraceClock() native "Timeline_getTraceClock";
 
 @patch
 int _getThreadCpuClock() native "Timeline_getThreadCpuClock";
 
 @patch
 int _getNextAsyncId() native "Timeline_getNextAsyncId";
 
 @patch
 int _getIsolateNum() native "Timeline_getIsolateNum";
 
 @patch
 void _reportTaskEvent(int start, int taskId, String phase, String category,
     String name, String argumentsAsJson) native "Timeline_reportTaskEvent";
 
 @patch
+void _reportBeginEvent(String name) native "Timeline_reportBeginEvent";
+
+@patch
 void _reportCompleteEvent(int start, int startCpu, String category, String name,
     String argumentsAsJson) native "Timeline_reportCompleteEvent";
 
 @patch
 void _reportInstantEvent(int start, String category, String name,
     String argumentsAsJson) native "Timeline_reportInstantEvent";