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

sdk/lib/developer/timeline.dart

Index: sdk/lib/developer/timeline.dart
diff --git a/sdk/lib/developer/timeline.dart b/sdk/lib/developer/timeline.dart
index 0b7cd41e6b8852544795335419037410933c3da5..4b4af546d1501a44b46d731be0ab39d6a5d7d644 100644
--- a/sdk/lib/developer/timeline.dart
+++ b/sdk/lib/developer/timeline.dart
@@ -225,7 +225,9 @@ class _SyncBlock {
   // The start time stamp of the thread cpu clock.
   final int _startCpu;
 
-  _SyncBlock._(this.name, this._start, this._startCpu);
+  _SyncBlock._(this.name, this._start, this._startCpu) {
+    _reportBeginEvent(name);
+  }
 
   /// Finish this block of time. At this point, this block can no longer be
   /// used.
@@ -279,6 +281,9 @@ external int _getIsolateNum();
 external void _reportTaskEvent(int start, int taskId, String phase,
     String category, String name, String argumentsAsJson);
 
+/// Reports a begin event for a synchronous event.
+external void _reportBeginEvent(String name);
+
 /// Reports a complete synchronous event.
 external void _reportCompleteEvent(int start, int startCpu, String category,
     String name, String argumentsAsJson);