Add initial version of retainers heap profile.

src/log.h

 // Copyright 2006-2008 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 203 matching lines @@
   // Emits a code delete event.
   static void CodeDeleteEvent(Address from);
 
   // ==== Events logged by --log-gc. ====
   // Heap sampling events: start, end, and individual types.
   static void HeapSampleBeginEvent(const char* space, const char* kind);
   static void HeapSampleEndEvent(const char* space, const char* kind);
   static void HeapSampleItemEvent(const char* type, int number, int bytes);
   static void HeapSampleJSConstructorEvent(const char* constructor,
                                            int number, int bytes);
+  static void HeapSampleJSRetainersEvent(const char* event);
   static void HeapSampleStats(const char* space, const char* kind,
                               int capacity, int used);
 
   static void SharedLibraryEvent(const char* library_path,
                                  uintptr_t start,
                                  uintptr_t end);
   static void SharedLibraryEvent(const wchar_t* library_path,
                                  uintptr_t start,
                                  uintptr_t end);
 
@@ skipping 104 matching lines @@
 // Class that extracts stack trace, used for profiling.
 class StackTracer : public AllStatic {
  public:
   static void Trace(TickSample* sample);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LOG_H_