Implemented an averaging object histogram in the vm.

runtime/vm/heap.h

 // Copyright (c) 2012, 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_HEAP_H_
 #define VM_HEAP_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/flags.h"
@@ skipping 194 matching lines @@
     Heap::GCReason reason_;
 
     class Data : public ValueObject {
     public:
       Data() {}
       int64_t micros_;
       intptr_t new_used_;
       intptr_t new_capacity_;
       intptr_t old_used_;
       intptr_t old_capacity_;
-
+    private:
       DISALLOW_COPY_AND_ASSIGN(Data);
     };
 
     enum {
       kDataEntries = 4
     };
 
     Data before_;
     Data after_;
     int64_t times_[kDataEntries];
     intptr_t data_[kDataEntries];
 
+   private:
     DISALLOW_COPY_AND_ASSIGN(GCStats);
   };
 
   static const intptr_t kNewAllocatableSize = 256 * KB;
 
   Heap();
 
   uword AllocateNew(intptr_t size);
   uword AllocateOld(intptr_t size, HeapPage::PageType type);
 
   // GC stats collection.
   void RecordBeforeGC(Space space, GCReason reason);
   void RecordAfterGC();
   void PrintStats();
+  void UpdateObjectHistogram();
 
   // The different spaces used for allocation.
   Scavenger* new_space_;
   PageSpace* old_space_;
 
   // GC stats collection.
   GCStats stats_;
 
   // This heap is in read-only mode: No allocation is allowed.
   bool read_only_;
@@ skipping 29 matching lines @@
   NoHeapGrowthControlScope();
   ~NoHeapGrowthControlScope();
  private:
   bool current_growth_controller_state_;
   DISALLOW_COPY_AND_ASSIGN(NoHeapGrowthControlScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_HEAP_H_