Add ability for embedder to provide private timeline trace data

runtime/vm/timeline.h

Index: runtime/vm/timeline.h
diff --git a/runtime/vm/timeline.h b/runtime/vm/timeline.h
index 002f8c9dc2f99018a53e4a24381d274777d86735..3bd32dd24c28dc8cd388a9340998da7d945b1288 100644
--- a/runtime/vm/timeline.h
+++ b/runtime/vm/timeline.h
@@ -5,6 +5,8 @@
 #ifndef VM_TIMELINE_H_
 #define VM_TIMELINE_H_
 
+#include "include/dart_tools_api.h"
+
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
 #include "vm/os.h"
@@ -65,17 +67,49 @@ class Timeline : public AllStatic {
     return &stream_##name##_enabled_;                                          \
   }                                                                            \
   static void SetStream##name##Enabled(bool enabled) {                         \
+    StreamStateChange(#name, stream_##name##_enabled_, enabled);               \
     stream_##name##_enabled_ = enabled;                                        \
   }
   ISOLATE_TIMELINE_STREAM_LIST(ISOLATE_TIMELINE_STREAM_FLAGS)
 #undef ISOLATE_TIMELINE_STREAM_FLAGS
   static void SetVMStreamEnabled(bool enabled);
 
+  static void set_start_recording_cb(
+      Dart_EmbedderTimelineStartRecording start_recording_cb) {
+    start_recording_cb_ = start_recording_cb;
+  }
+
+  static Dart_EmbedderTimelineStartRecording get_start_recording_cb() {
+    return start_recording_cb_;
+  }
+
+  static void set_stop_recording_cb(
+      Dart_EmbedderTimelineStopRecording stop_recording_cb) {
+    stop_recording_cb_ = stop_recording_cb;
+  }
+
+  static Dart_EmbedderTimelineStopRecording get_stop_recording_cb() {
+    return stop_recording_cb_;
+  }
+
+  static void set_get_timeline_cb(
+      Dart_EmbedderTimelineGetTimeline get_timeline_cb) {
+    get_timeline_cb_ = get_timeline_cb;
+  }
+
+  static Dart_EmbedderTimelineGetTimeline get_get_timeline_cb() {
+    return get_timeline_cb_;
+  }
+
  private:
+  static void StreamStateChange(const char* stream_name, bool prev, bool curr);
   static TimelineEventRecorder* recorder_;
   static TimelineStream vm_stream_;
   static TimelineStream vm_api_stream_;
   static MallocGrowableArray<char*>* enabled_streams_;
+  static Dart_EmbedderTimelineStartRecording start_recording_cb_;
+  static Dart_EmbedderTimelineStopRecording stop_recording_cb_;
+  static Dart_EmbedderTimelineGetTimeline get_timeline_cb_;
 
 #define ISOLATE_TIMELINE_STREAM_DECLARE_FLAG(name, not_used)                   \
   static bool stream_##name##_enabled_;