Implement TracePathToObjectFrom helper for debugging.

src/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 6752 matching lines @@
       Object* obj = object_stack_[i];
       obj->Print();
     }
     PrintF("=====================================\n");
   }
 }
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 
 #ifdef DEBUG
+// Triggers a depth-first traversal of reachable objects from one
+// given root object and finds a path to a specific heap object and
+// prints it.
+void Heap::TracePathToObjectFrom(Object* target, Object* root) {
+  PathTracer tracer(target, PathTracer::FIND_ALL, VISIT_ALL);
+  tracer.VisitPointer(&root);
+}
+
+
 // Triggers a depth-first traversal of reachable objects from roots
 // and finds a path to a specific heap object and prints it.
 void Heap::TracePathToObject(Object* target) {
   PathTracer tracer(target, PathTracer::FIND_ALL, VISIT_ALL);
   IterateRoots(&tracer, VISIT_ONLY_STRONG);
 }
 
 
 // Triggers a depth-first traversal of reachable objects from roots
 // and finds a path to any global object and prints it. Useful for
@@ skipping 446 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   memcpy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   memcpy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal