Update V8 to r6190 as required by WebKit r75315

Change-Id: I0b2f598e4d8748df417ad350fc47a1c465ad1fef
diff --git a/src/factory.cc b/src/factory.cc
index 83af447..2bc878c 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -99,6 +99,14 @@
   CALL_HEAP_FUNCTION(Heap::LookupSymbol(string), String);
 }
 
+Handle<String> Factory::LookupAsciiSymbol(Vector<const char> string) {
+  CALL_HEAP_FUNCTION(Heap::LookupAsciiSymbol(string), String);
+}
+
+Handle<String> Factory::LookupTwoByteSymbol(Vector<const uc16> string) {
+  CALL_HEAP_FUNCTION(Heap::LookupTwoByteSymbol(string), String);
+}
+
 
 Handle<String> Factory::NewStringFromAscii(Vector<const char> string,
                                            PretenureFlag pretenure) {