Add message sizing to basic IPC traits and struct macros.

mojo/public/cpp/bindings/tests/pickled_struct_blink.cc

Index: mojo/public/cpp/bindings/tests/pickled_struct_blink.cc
diff --git a/mojo/public/cpp/bindings/tests/pickled_struct_blink.cc b/mojo/public/cpp/bindings/tests/pickled_struct_blink.cc
index 602f15aefb50dc2f8bbd7aa8dc8106a785b2c4cf..57a191516ddd0e01889f0510779f39507b444c0e 100644
--- a/mojo/public/cpp/bindings/tests/pickled_struct_blink.cc
+++ b/mojo/public/cpp/bindings/tests/pickled_struct_blink.cc
@@ -25,6 +25,13 @@ PickledStructBlink::~PickledStructBlink() {}
 
 namespace IPC {
 
+void ParamTraits<mojo::test::PickledStructBlink>::GetSize(
+    base::PickleSizer* sizer,
+    const param_type& p) {
+  sizer->AddInt();
+  sizer->AddInt();
+}
+
 void ParamTraits<mojo::test::PickledStructBlink>::Write(base::Pickle* m,
                                                         const param_type& p) {
   m->WriteInt(p.foo());