Add message sizing to basic IPC traits and struct macros.

base/files/file_path.h

Index: base/files/file_path.h
diff --git a/base/files/file_path.h b/base/files/file_path.h
index 89e9cbfb1d5c3d98cfbc4fc6edf5baebf200e93c..4eb712af0540cf503676e3b012487c8d5fbb4650 100644
--- a/base/files/file_path.h
+++ b/base/files/file_path.h
@@ -138,6 +138,7 @@ namespace base {
 
 class Pickle;
 class PickleIterator;
+class PickleSizer;
 
 // An abstraction to isolate users from the differences between native
 // pathnames on different platforms.
@@ -377,6 +378,7 @@ class BASE_EXPORT FilePath {
   // Similar to FromUTF8Unsafe, but accepts UTF-16 instead.
   static FilePath FromUTF16Unsafe(const string16& utf16);
 
+  void GetSizeForPickle(PickleSizer* sizer) const;
   void WriteToPickle(Pickle* pickle) const;
   bool ReadFromPickle(PickleIterator* iter);