Update V8 to r5091 as required by WebKit r63859.

Change-Id: I8e35d765e6f6c7f89eccff900e1cabe2d5dd6110
diff --git a/src/mips/codegen-mips.h b/src/mips/codegen-mips.h
index 0f0a746..3ad94e8 100644
--- a/src/mips/codegen-mips.h
+++ b/src/mips/codegen-mips.h
@@ -355,6 +355,7 @@
   void GenerateRandomHeapNumber(ZoneList<Expression*>* args);
 
   void GenerateIsObject(ZoneList<Expression*>* args);
+  void GenerateIsSpecObject(ZoneList<Expression*>* args);
   void GenerateIsFunction(ZoneList<Expression*>* args);
   void GenerateIsUndetectableObject(ZoneList<Expression*>* args);
   void GenerateStringAdd(ZoneList<Expression*>* args);