Add message sizing to basic IPC traits and struct macros.

mojo/public/cpp/bindings/tests/pickled_struct_chromium.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_TESTS_PICKLED_STRUCT_CHROMIUM_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_TESTS_PICKLED_STRUCT_CHROMIUM_H_
 
 #include <stddef.h>
 
 #include <string>
 
 #include "base/macros.h"
 #include "ipc/ipc_param_traits.h"
 
 namespace base {
 class Pickle;
 class PickleIterator;
+class PickleSizer;
 }
 
 namespace mojo {
 namespace test {
 
 // An implementation of a hypothetical PickledStruct type specifically for
 // consumers in the greater Chromium tree.
 class PickledStructChromium {
  public:
   PickledStructChromium();
@@ skipping 20 matching lines @@
 
 }  // namespace test
 }  // namespace mojo
 
 namespace IPC {
 
 template <>
 struct ParamTraits<mojo::test::PickledStructChromium> {
   using param_type = mojo::test::PickledStructChromium;
 
-  static size_t GetSize(const param_type& p) { return 8; }
+  static void GetSize(base::PickleSizer* sizer, const param_type& p);
   static void Write(base::Pickle* m, const param_type& p);
   static bool Read(const base::Pickle* m,
                    base::PickleIterator* iter,
                    param_type* r);
   static void Log(const param_type& p, std::string* l) {}
 };
 
 }  // namespace IPC
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_TESTS_PICKLED_STRUCT_CHROMIUM_H_