Make a NaClDesc ctor for creating descs from NaClFileInfo.

src/public/nacl_file_info.h

Index: src/public/nacl_file_info.h
diff --git a/src/trusted/validator/nacl_file_info.h b/src/public/nacl_file_info.h
similarity index 72%
copy from src/trusted/validator/nacl_file_info.h
copy to src/public/nacl_file_info.h
index f93796bac2cbf553071a40899ac1d563310303f7..0c103bdfa1849ca5143e08d1e18d2e6949a3cbec 100644
--- a/src/trusted/validator/nacl_file_info.h
+++ b/src/public/nacl_file_info.h
@@ -4,8 +4,8 @@
  * found in the LICENSE file.
  */
 
-#ifndef NATIVE_CLIENT_SRC_TRUSTED_REVERSE_SERVICE_NACL_FILE_INFO_H_
-#define NATIVE_CLIENT_SRC_TRUSTED_REVERSE_SERVICE_NACL_FILE_INFO_H_
+#ifndef NATIVE_CLIENT_SRC_PUBLIC_NACL_FILE_INFO_H_
+#define NATIVE_CLIENT_SRC_PUBLIC_NACL_FILE_INFO_H_
 
 #include "native_client/src/include/nacl_base.h"
 #include "native_client/src/include/portability.h"
@@ -22,6 +22,10 @@ struct NaClFileToken {
   uint64_t hi;
 };
 
+static INLINE int NaClFileTokenIsValid(struct NaClFileToken *file_token) {
+  return !(file_token->lo == 0 && file_token->hi == 0);
+}
+
 struct NaClFileInfo {
   /* desc is either a Unix file descriptor or a Windows file handle. */
   int32_t desc;
@@ -30,4 +34,4 @@ struct NaClFileInfo {
 
 EXTERN_C_END
 
-#endif /* NATIVE_CLIENT_SRC_TRUSTED_REVERSE_SERVICE_NACL_FILE_INFO_H_ */
+#endif /* NATIVE_CLIENT_SRC_PUBLIC_NACL_FILE_INFO_H_ */