Generate param traits size methods for IPC files in chrome/ (and traits it depends on).

media/gpu/ipc/common/media_messages.h

Index: media/gpu/ipc/common/media_messages.h
diff --git a/media/gpu/ipc/common/media_messages.h b/media/gpu/ipc/common/media_messages.h
index 780e378cc6c4cad7914949a1c141d832db7dfaa9..6c128a63ec31e026a5c90a0775c7f53962b832f6 100644
--- a/media/gpu/ipc/common/media_messages.h
+++ b/media/gpu/ipc/common/media_messages.h
@@ -25,6 +25,7 @@ namespace IPC {
 template <>
 struct ParamTraits<media::BitstreamBuffer> {
   using param_type = media::BitstreamBuffer;
+  static void GetSize(base::PickleSizer* s, const param_type& p);
   static void Write(base::Pickle* m, const param_type& p);
   static bool Read(const base::Pickle* m,
                    base::PickleIterator* iter,