Update V8 to r6768 as required by WebKit r78450

Change-Id: Ib8868ff7147a76547a8d1d85f257ebe8546a3d3f
diff --git a/src/serialize.cc b/src/serialize.cc
index 6a6c6bb..f8e98d3 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -192,7 +192,7 @@
   { BUILTIN, \
     Builtins::name, \
     "Builtins::" #name },
-#define DEF_ENTRY_A(name, kind, state) DEF_ENTRY_C(name, ignored)
+#define DEF_ENTRY_A(name, kind, state, extra) DEF_ENTRY_C(name, ignored)
 
   BUILTIN_LIST_C(DEF_ENTRY_C)
   BUILTIN_LIST_A(DEF_ENTRY_A)
@@ -335,7 +335,7 @@
 
   Add(ExternalReference::delete_handle_scope_extensions().address(),
       RUNTIME_ENTRY,
-      3,
+      4,
       "HandleScope::DeleteExtensions");
 
   // Miscellaneous
@@ -504,7 +504,7 @@
       "power_double_int_function");
   Add(ExternalReference::arguments_marker_location().address(),
       UNCLASSIFIED,
-      40,
+      41,
       "Factory::arguments_marker().location()");
 }