- Assert that we do not hold the timeline lock while entering

runtime/vm/timeline.h

Index: runtime/vm/timeline.h
diff --git a/runtime/vm/timeline.h b/runtime/vm/timeline.h
index 61759ddb523d800880f9e7b7c241ca4e367f295d..fa55f75f884a75df9dfb4385866ed55c59047ec4 100644
--- a/runtime/vm/timeline.h
+++ b/runtime/vm/timeline.h
@@ -236,16 +236,6 @@ class TimelineEvent {
   const char* GetSerializedJSON() const;
 
  private:
-  int64_t timestamp0_;
-  int64_t timestamp1_;
-  TimelineEventArgument* arguments_;
-  intptr_t arguments_length_;
-  uword state_;
-  const char* label_;
-  const char* category_;
-  ThreadId thread_;
-  Dart_Port isolate_id_;
-
   void FreeArguments();
 
   void StreamInit(TimelineStream* stream);
@@ -257,6 +247,15 @@ class TimelineEvent {
     state_ = EventTypeField::update(event_type, state_);
   }
 
+  void set_timestamp0(int64_t value) {
+    ASSERT(timestamp0_ == 0);
+    timestamp0_ = value;
+  }
+  void set_timestamp1(int64_t value) {
+    ASSERT(timestamp1_ == 0);
+    timestamp1_ = value;
+  }
+
   enum StateBits {
     kEventTypeBit = 0,  // reserve 4 bits for type.
     kNextBit = 4,
@@ -264,6 +263,16 @@ class TimelineEvent {
 
   class EventTypeField : public BitField<EventType, kEventTypeBit, 4> {};
 
+  int64_t timestamp0_;
+  int64_t timestamp1_;
+  TimelineEventArgument* arguments_;
+  intptr_t arguments_length_;
+  uword state_;
+  const char* label_;
+  const char* category_;
+  ThreadId thread_;
+  Dart_Port isolate_id_;
+
   friend class TimelineEventRecorder;
   friend class TimelineEventEndlessRecorder;
   friend class TimelineEventRingRecorder;