Add basic infrastructure for protecting V8's heap when leaving the VM...

src/globals.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 341 matching lines @@
 // A StateTag represents a possible state of the VM.  When compiled with
 // ENABLE_LOGGING_AND_PROFILING, the logger maintains a stack of these.
 // Creating a VMState object enters a state by pushing on the stack, and
 // destroying a VMState object leaves a state by popping the current state
 // from the stack.
 
 #define STATE_TAG_LIST(V) \
   V(JS)                   \
   V(GC)                   \
   V(COMPILER)             \
-  V(OTHER)
+  V(OTHER)                \
+  V(EXTERNAL)
 
 enum StateTag {
 #define DEF_STATE_TAG(name) name,
   STATE_TAG_LIST(DEF_STATE_TAG)
 #undef DEF_STATE_TAG
   // Pseudo-types.
   state_tag_count
 };
 
 
@@ skipping 136 matching lines @@
 
   Dest dest;
   memcpy(&dest, &source, sizeof(dest));
   return dest;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_GLOBALS_H_