Split extra checks into extra checks and handle zapping

Makefile

 # 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 58 matching lines @@
   GYPFLAGS += -Dv8_enable_backtrace=0
 else
   GYPFLAGS += -Dv8_enable_backtrace=1
 endif
 # snapshot=off
 ifeq ($(snapshot), off)
   GYPFLAGS += -Dv8_use_snapshot='false'
 endif
 # extrachecks=on/off
 ifeq ($(extrachecks), on)
-  GYPFLAGS += -Dv8_enable_extra_checks=1
+  GYPFLAGS += -Dv8_enable_extra_checks=1 -Dv8_enable_handle_zapping=1
 endif
 ifeq ($(extrachecks), off)
-  GYPFLAGS += -Dv8_enable_extra_checks=0
+  GYPFLAGS += -Dv8_enable_extra_checks=0 -Dv8_enable_handle_zapping=0
 endif
 # gdbjit=on/off
 ifeq ($(gdbjit), on)
   GYPFLAGS += -Dv8_enable_gdbjit=1
 endif
 ifeq ($(gdbjit), off)
   GYPFLAGS += -Dv8_enable_gdbjit=0
 endif
 # vtunejit=on
 ifeq ($(vtunejit), on)
@@ skipping 317 matching lines @@
         @$(OUTDIR)/ia32.release/d8 --dump-heap-constants >> $(DUMP_FILE)
 
 # Dependencies.
 # Remember to keep these in sync with the DEPS file.
 dependencies:
         svn checkout --force http://gyp.googlecode.com/svn/trunk build/gyp \
             --revision 1685
         svn checkout --force \
             https://src.chromium.org/chrome/trunk/deps/third_party/icu46 \
             third_party/icu --revision 214189