Disable PGO for ObjectImpl::nativeLookup (bug 844580, r=billm).

js/src/vm/ObjectImpl.cpp

@@ -282,6 +282,11 @@ js::ObjectImpl::slotInRange(uint32_t slot, SentinelAllowed sentinel) const
 }
 #endif /* DEBUG */
 
+// See bug 844580.
+#if defined(_MSC_VER)
+# pragma optimize("g", off)
+#endif
+
 #if defined(_MSC_VER) && _MSC_VER >= 1500
 /*
  * Work around a compiler bug in MSVC9 and above, where inlining this function
@@ -298,6 +303,10 @@ js::ObjectImpl::nativeLookup(JSContext *cx, jsid id)
     return Shape::search(cx, lastProperty(), id, &spp);
 }
 
+#if defined(_MSC_VER)
+# pragma optimize("", on)
+#endif
+
 void
 js::ObjectImpl::markChildren(JSTracer *trc)
 {