Update V8 to r6768 as required by WebKit r78450

Change-Id: Ib8868ff7147a76547a8d1d85f257ebe8546a3d3f
diff --git a/test/mjsunit/compiler/regress-arguments.js b/test/mjsunit/compiler/regress-arguments.js
index 234d3fb..ebae5a0 100644
--- a/test/mjsunit/compiler/regress-arguments.js
+++ b/test/mjsunit/compiler/regress-arguments.js
@@ -46,4 +46,7 @@
  return f.apply(v, arguments);
 }
 
-for (var i=0; i<1000000; i++) assertEquals(void 0, u());
+Number.prototype.foo = 42;
+delete Number.prototype.foo;
+
+for (var i=0; i<100000; i++) assertEquals(void 0, u());