Update V8 to r6768 as required by WebKit r78450

Change-Id: Ib8868ff7147a76547a8d1d85f257ebe8546a3d3f
diff --git a/src/compilation-cache.h b/src/compilation-cache.h
index 37e21be..f779a23 100644
--- a/src/compilation-cache.h
+++ b/src/compilation-cache.h
@@ -51,7 +51,8 @@
   // contain a script for the given source string.
   static Handle<SharedFunctionInfo> LookupEval(Handle<String> source,
                                                Handle<Context> context,
-                                               bool is_global);
+                                               bool is_global,
+                                               StrictModeFlag strict_mode);
 
   // Returns the regexp data associated with the given regexp if it
   // is in cache, otherwise an empty handle.