Add flag to trace object groups

src/global-handles.h

 // Copyright 2011 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_GLOBAL_HANDLES_H_
 #define V8_GLOBAL_HANDLES_H_
 
 #include "include/v8.h"
 #include "include/v8-profiler.h"
 
@@ skipping 224 matching lines @@
 
   // Identify unmodified objects that are in weak state and marks them
   // unmodified
   void IdentifyWeakUnmodifiedObjects(WeakSlotCallback is_unmodified);
 
   // Iterate over objects in object groups that have at least one object
   // which requires visiting. The callback has to return true if objects
   // can be skipped and false otherwise.
   bool IterateObjectGroups(ObjectVisitor* v, WeakSlotCallbackWithHeap can_skip);
 
+  // Print all objects in object groups
+  void PrintObjectGroups();
+
   // Add an object group.
   // Should be only used in GC callback function before a collection.
   // All groups are destroyed after a garbage collection.
   void AddObjectGroup(Object*** handles,
                       size_t length,
                       v8::RetainedObjectInfo* info);
 
   // Associates handle with the object group represented by id.
   // Should be only used in GC callback function before a collection.
   // All groups are destroyed after a garbage collection.
@@ skipping 197 matching lines @@
   int singleton_handles_[NUMBER_OF_SINGLETON_HANDLES];
 
   DISALLOW_COPY_AND_ASSIGN(EternalHandles);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_GLOBAL_HANDLES_H_