[NaCl SDK] nacl_io: big refactor to return error value (errno).

native_client_sdk/src/libraries/nacl_io/kernel_proxy.h

Index: native_client_sdk/src/libraries/nacl_io/kernel_proxy.h
diff --git a/native_client_sdk/src/libraries/nacl_io/kernel_proxy.h b/native_client_sdk/src/libraries/nacl_io/kernel_proxy.h
index 6c7b6b31e91aab95be47ead7e8ac8c643f395885..e8c251a32ab2e8b0d5754a766bb0f9965e3f9915 100644
--- a/native_client_sdk/src/libraries/nacl_io/kernel_proxy.h
+++ b/native_client_sdk/src/libraries/nacl_io/kernel_proxy.h
@@ -24,9 +24,12 @@ class PepperInterface;
 
 // KernelProxy provide one-to-one mapping for libc kernel calls.  Calls to the
 // proxy will result in IO access to the provided Mount and MountNode objects.
+//
+// NOTE: The KernelProxy is the only class that should be setting errno. All
+// other classes should return Error (as defined by nacl_io/error.h).
 class KernelProxy : protected KernelObject {
  public:
-  typedef Mount* (*MountFactory_t)(int, StringMap_t&, PepperInterface*);
+  typedef Error (*MountFactory_t)(int, StringMap_t&, PepperInterface*, Mount**);
   typedef std::map<std::string, std::string> StringMap_t;
   typedef std::map<std::string, MountFactory_t> MountFactoryMap_t;