Implement heap profiler memory usage reporting.

src/profile-generator.h

Index: src/profile-generator.h
diff --git a/src/profile-generator.h b/src/profile-generator.h
index 45dc9a4a44daca80969eb70e7c19b9c7e1a0be84..d56d874705da50fa7320ab01dd5f0cfe808b09eb 100644
--- a/src/profile-generator.h
+++ b/src/profile-generator.h
@@ -72,6 +72,7 @@ class StringsStorage {
   const char* GetName(int index);
   inline const char* GetFunctionName(String* name);
   inline const char* GetFunctionName(const char* name);
+  size_t GetUsedMemorySize() const;
 
  private:
   static const int kMaxNameSize = 1024;
@@ -650,6 +651,7 @@ class HeapObjectsMap {
 
   void StopHeapObjectsTracking();
   SnapshotObjectId PushHeapObjectsStats(OutputStream* stream);
+  size_t GetUsedMemorySize() const;
 
   static SnapshotObjectId GenerateId(v8::RetainedObjectInfo* info);
   static inline SnapshotObjectId GetNthGcSubrootId(int delta);
@@ -734,6 +736,7 @@ class HeapSnapshotsCollection {
   SnapshotObjectId last_assigned_id() const {
     return ids_.last_assigned_id();
   }
+  size_t GetUsedMemorySize() const;
 
  private:
   INLINE(static bool HeapSnapshotsMatch(void* key1, void* key2)) {