Update V8 to r6768 as required by WebKit r78450

Change-Id: Ib8868ff7147a76547a8d1d85f257ebe8546a3d3f
diff --git a/src/arm/codegen-arm.h b/src/arm/codegen-arm.h
index 589e704..8f46256 100644
--- a/src/arm/codegen-arm.h
+++ b/src/arm/codegen-arm.h
@@ -287,6 +287,7 @@
   // Accessors
   inline bool is_eval();
   inline Scope* scope();
+  inline StrictModeFlag strict_mode_flag();
 
   // Generating deferred code.
   void ProcessDeferred();