NaCl: Address some TODOs from moving PPAPI IRT interface into the Chromium repo

ppapi/nacl_irt/irt_ppapi.h

Index: ppapi/nacl_irt/irt_ppapi.h
diff --git a/ppapi/nacl_irt/irt_ppapi.h b/ppapi/nacl_irt/irt_ppapi.h
index d1cbbee8cb862ccb9d5263b7b43c1bb7d6840cfa..344e10c1b33380ddd9d0f788749d3bef1abb2d4e 100644
--- a/ppapi/nacl_irt/irt_ppapi.h
+++ b/ppapi/nacl_irt/irt_ppapi.h
@@ -33,12 +33,6 @@ struct PP_ThreadFunctions {
   int (*thread_join)(uintptr_t tid);
 };
 
-/*
- * TODO(mseaborn): Make this unconditional after the definition of the
- * struct has been removed from the NaCl side's irt.h.
- */
-#if !defined(NACL_IRT_PPAPIHOOK_v0_1)
-
 #define NACL_IRT_PPAPIHOOK_v0_1 "nacl-irt-ppapihook-0.1"
 struct nacl_irt_ppapihook {
   int (*ppapi_start)(const struct PP_StartFunctions*);
@@ -46,5 +40,3 @@ struct nacl_irt_ppapihook {
 };
 
 #endif
-
-#endif