Add Function based profile tree

runtime/vm/profiler_service.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_PROFILER_SERVICE_H_
 #define VM_PROFILER_SERVICE_H_
 
 #include "vm/allocation.h"
 #include "vm/code_observers.h"
 #include "vm/globals.h"
@@ skipping 15 matching lines @@
   enum TagOrder {
     kNoTags,
     kUser,
     kUserVM,
     kVM,
     kVMUser
   };
 
   static void PrintJSON(JSONStream* stream,
                         TagOrder tag_order);
+
+  static void ClearSamples();
 };
 
 }  // namespace dart
 
 #endif  // VM_PROFILER_SERVICE_H_