Update V8 to r3431 as required by WebKit r51976.

Change-Id: I567392c3f8c0a0d5201a4249611ac4ccf468cd5b
diff --git a/src/api.h b/src/api.h
index 1221f35..a28e1f0 100644
--- a/src/api.h
+++ b/src/api.h
@@ -125,6 +125,15 @@
 }
 
 
+class ApiFunction {
+ public:
+  explicit ApiFunction(v8::internal::Address addr) : addr_(addr) { }
+  v8::internal::Address address() { return addr_; }
+ private:
+  v8::internal::Address addr_;
+};
+
+
 v8::Arguments::Arguments(v8::Local<v8::Value> data,
                          v8::Local<v8::Object> holder,
                          v8::Local<v8::Function> callee,