Ensure TimelineEventRingRecorder outputs blocks in increasing time order

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"
 
@@ skipping 375 matching lines @@
   void PrintJSON(JSONStream* js);
   TimelineEventBlock* GetNewBlock();
   TimelineEventBlock* GetHeadBlock();
 
  protected:
   void VisitObjectPointers(ObjectPointerVisitor* visitor);
   TimelineEvent* StartEvent(const Object& object);
   TimelineEvent* StartEvent();
   void CompleteEvent(TimelineEvent* event);
 
+  intptr_t FindOldestBlockIndex() const;
   TimelineEventBlock* GetNewBlockLocked();
 
   void PrintJSONEvents(JSONArray* array) const;
 
   TimelineEventBlock** blocks_;
   RawArray* event_objects_;
   intptr_t capacity_;
   intptr_t num_blocks_;
   intptr_t block_cursor_;
 };
@@ skipping 76 matching lines @@
   }
 
  private:
   TimelineEventBlock* current_;
   TimelineEventRecorder* recorder_;
 };
 
 }  // namespace dart
 
 #endif  // VM_TIMELINE_H_