Merge WebKit at r59636: Update v8 to r4660.

Will build and run with current webkit.

Change-Id: I57bae621fd894da363ba84e1757ad09eb7c502b9
diff --git a/test/mjsunit/mjsunit.js b/test/mjsunit/mjsunit.js
index 07c4e7e..558282f 100644
--- a/test/mjsunit/mjsunit.js
+++ b/test/mjsunit/mjsunit.js
@@ -27,6 +27,8 @@
 
 function MjsUnitAssertionError(message) {
   this.message = message;
+  // This allows fetching the stack trace using TryCatch::StackTrace.
+  this.stack = new Error("").stack;
 }
 
 MjsUnitAssertionError.prototype.toString = function () {