Add option to compute average scavenge speed w.r.t survived objects.

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 1259 matching lines @@
   inline void IncrementPromotedObjectsSize(int object_size) {
     DCHECK(object_size > 0);
     promoted_objects_size_ += object_size;
   }
 
   inline void IncrementSemiSpaceCopiedObjectSize(int object_size) {
     DCHECK(object_size > 0);
     semi_space_copied_object_size_ += object_size;
   }
 
+  inline intptr_t SurvivedNewSpaceObjectSize() {
+    return promoted_objects_size_ + semi_space_copied_object_size_;
+  }
+
   inline void IncrementNodesDiedInNewSpace() { nodes_died_in_new_space_++; }
 
   inline void IncrementNodesCopiedInNewSpace() { nodes_copied_in_new_space_++; }
 
   inline void IncrementNodesPromoted() { nodes_promoted_++; }
 
   inline void IncrementYoungSurvivorsCounter(int survived) {
     DCHECK(survived >= 0);
     survived_last_scavenge_ = survived;
     survived_since_last_expansion_ += survived;
@@ skipping 1542 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_