Update V8 to r5017 as required by WebKit r62496

Change-Id: I1b4b7718d1d77ceef07f543e9150a2cb3a628f3a
diff --git a/src/factory.h b/src/factory.h
index 8a190fa..b0a0571 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -180,6 +180,10 @@
 
   static Handle<Map> CopyMapDropTransitions(Handle<Map> map);
 
+  static Handle<Map> GetFastElementsMap(Handle<Map> map);
+
+  static Handle<Map> GetSlowElementsMap(Handle<Map> map);
+
   static Handle<FixedArray> CopyFixedArray(Handle<FixedArray> array);
 
   // Numbers (eg, literals) are pretenured by the parser.