Update V8 to r7079 as required by WebKit r80534.

Change-Id: I487c152e485d5a40b68997d7c0d2f1fba5da0834
diff --git a/src/arguments.h b/src/arguments.h
index d51c9e4..5cf8dea 100644
--- a/src/arguments.h
+++ b/src/arguments.h
@@ -78,7 +78,7 @@
 class CustomArguments : public Relocatable {
  public:
   inline CustomArguments(Object* data,
-                         JSObject* self,
+                         Object* self,
                          JSObject* holder) {
     values_[2] = self;
     values_[1] = holder;