Implement safepointing of threads

runtime/vm/timeline.h

 // 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.
 
 #ifndef VM_TIMELINE_H_
 #define VM_TIMELINE_H_
 
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
 #include "vm/os.h"
@@ skipping 512 matching lines @@
   intptr_t block_index_;
 
   // Only accessed under the recorder's lock.
   ThreadId thread_id_;
   bool in_use_;
 
   void Open();
   void Finish();
 
   friend class Thread;
-  friend class ThreadRegistry;
   friend class TimelineEventRecorder;
   friend class TimelineEventRingRecorder;
   friend class TimelineEventEndlessRecorder;
   friend class TimelineTestHelper;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TimelineEventBlock);
 };
 
 
@@ skipping 199 matching lines @@
 
  private:
   TimelineEventBlock* current_;
   TimelineEventRecorder* recorder_;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_TIMELINE_H_