Copy event label.

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 "include/dart_tools_api.h"
 
 #include "vm/allocation.h"
@@ skipping 312 matching lines @@
 
   class EventTypeField : public BitField<uword, EventType, kEventTypeBit, 4> {};
   class PreSerializedJSON :
       public BitField<uword, bool, kPreSerializedJSON, 1> {};
 
   int64_t timestamp0_;
   int64_t timestamp1_;
   TimelineEventArgument* arguments_;
   intptr_t arguments_length_;
   uword state_;
-  const char* label_;
+  char* label_;
   const char* category_;
   ThreadId thread_;
   Dart_Port isolate_id_;
 
   friend class TimelineEventRecorder;
   friend class TimelineEventEndlessRecorder;
   friend class TimelineEventRingRecorder;
   friend class TimelineEventStartupRecorder;
   friend class TimelineStream;
   friend class TimelineTestHelper;
@@ skipping 494 matching lines @@
 
  private:
   TimelineEventBlock* current_;
   TimelineEventRecorder* recorder_;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_TIMELINE_H_