Add --timing

runtime/vm/thread.cc

Index: runtime/vm/thread.cc
diff --git a/runtime/vm/thread.cc b/runtime/vm/thread.cc
index 6e203b1d083d12d4fd9dd3ce5cd12987053ccd9c..ceba83f06b9858c6f0a2d7a69d3a68b3dc0a505d 100644
--- a/runtime/vm/thread.cc
+++ b/runtime/vm/thread.cc
@@ -342,6 +342,14 @@ bool Thread::IsThreadInterrupterEnabled(ThreadInterruptCallback* callback,
 }
 
 
+void Thread::CloseTimelineBlock() {
+  if (timeline_block() != NULL) {
+    timeline_block()->Finish();
+    set_timeline_block(NULL);
+  }
+}
+
+
 bool Thread::CanLoadFromThread(const Object& object) {
 #define CHECK_OBJECT(type_name, member_name, expr, default_init_value)         \
   if (object.raw() == expr) return true;
@@ -361,6 +369,7 @@ CACHED_VM_OBJECTS_LIST(COMPUTE_OFFSET)
   return -1;
 }
 
+
 intptr_t Thread::OffsetFromThread(const RuntimeEntry* runtime_entry) {
 #define COMPUTE_OFFSET(name)                                                   \
   if (runtime_entry->function() == k##name##RuntimeEntry.function())         { \