Make a NaClDesc ctor for creating descs from NaClFileInfo.

src/trusted/desc/nacl_desc_wrapper.h

Index: src/trusted/desc/nacl_desc_wrapper.h
diff --git a/src/trusted/desc/nacl_desc_wrapper.h b/src/trusted/desc/nacl_desc_wrapper.h
index e332ca1467664cebaf0f29b32e8cf8c61927ea69..0ff8af593177df559e815783fb16733c42916b0b 100644
--- a/src/trusted/desc/nacl_desc_wrapper.h
+++ b/src/trusted/desc/nacl_desc_wrapper.h
@@ -6,6 +6,7 @@
 #define NATIVE_CLIENT_SRC_TRUSTED_DESC_NACL_DESC_WRAPPER_H_
 
 #include "native_client/src/include/nacl_base.h"
+#include "native_client/src/public/nacl_file_info.h"
 #include "native_client/src/trusted/desc/nacl_desc_base.h"
 #include "native_client/src/trusted/desc/nrd_xfer.h"
 
@@ -29,6 +30,9 @@ class DescWrapperFactory {
   DescWrapper* MakeImcSock(NaClHandle handle);
   // Create a file descriptor object.
   DescWrapper* MakeFileDesc(int host_os_desc, int mode);
+  // As with MakeFileDesc, but with NaClFileInfo metadata.
+  DescWrapper* MakeFileDescMetadata(struct NaClFileInfo file_info,

[Mark Seaborn, 2014/05/02 20:50:40]

Is it your intention to use this new method from the Chromium side?

The reason I ask is that DescWrapper is quite deprecated, so it would be
preferable to add a C constructor that returns a NaClDesc* (and if necessary add
a NaClDesc -> DescWrapper constructor).

[jvoung (off chromium), 2014/05/14 23:42:47]

Yes, this was to make the desc and token ownership transfer happen in one
function call, instead of having separate function calls:

https://codereview.chromium.org/263683002/diff/1/ppapi/native_client/src/trus...
Okay, I didn't know that DescWrapper was deprecated.  The current plugin code
still uses that, so it seemed to match better.

I've add a C constructor (well mostly just calls the nacl_desc_io one) and use
that here to make the DescWrapper.

+                                    int mode);
   // As with MakeFileDesc, but with quota management.
   DescWrapper* MakeFileDescQuota(int host_os_desc, int mode,
                                  const uint8_t* file_id);