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

ppapi/proxy/ppapi_messages.cc

Index: ppapi/proxy/ppapi_messages.cc
diff --git a/ppapi/proxy/ppapi_messages.cc b/ppapi/proxy/ppapi_messages.cc
index 5cee1c78254ef6138046b0fdce52f49637c67777..6ed361b21113455225fdb4a8ccb5b886d212bca2 100644
--- a/ppapi/proxy/ppapi_messages.cc
+++ b/ppapi/proxy/ppapi_messages.cc
@@ -14,6 +14,12 @@
 #include "ipc/struct_destructor_macros.h"
 #include "ppapi/proxy/ppapi_messages.h"
 
+// Generate param traits size methods.
+#include "ipc/param_traits_size_macros.h"
+namespace IPC {
+#include "ppapi/proxy/ppapi_messages.h"
+}
+
 // Generate param traits write methods.
 #include "ipc/param_traits_write_macros.h"
 namespace IPC {