EDK: Add Core::DuplicateHandleWithReducedRights().

mojo/public/c/system/handle.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains Mojo system handle-related declarations/definitions.
 //
 // Note: This header should be compilable as C.
 
 #ifndef MOJO_PUBLIC_C_SYSTEM_HANDLE_H_
 #define MOJO_PUBLIC_C_SYSTEM_HANDLE_H_
@@ skipping 124 matching lines @@
 //
 // Note that it is not an error to "remove" rights that the handle does not
 // (currently) possess.
 //
 // Returns:
 //   |MOJO_RESULT_OK| on success.
 //   |MOJO_RESULT_INVALID_ARGUMENT| if |handle| is not a valid handle.
 //   |MOJO_RESULT_BUSY| if |handle| is currently in use in some transaction
 //       (that, e.g., may result in it being invalidated, such as being sent in
 //       a message).
+//
+// TODO(vtl): Discuss this API some more. It may be more desirable to replace
+// the handle with a new one (with reduced rights).
 MojoResult MojoReduceRights(MojoHandle handle,
                             MojoHandleRights rights_to_remove);
 
 // |MojoDuplicateHandleWithReducedRights()|: Duplicates |handle| to a new handle
 // with reduced rights. This requires |handle| to have the
 // |MOJO_HANDLE_RIGHT_DUPLICATE| (note that some handle types may never have
 // this right).
 //
 // The rights for the new handle are determined as in |MojoReduceRights()|. That
 // is, on success:
@@ skipping 29 matching lines @@
 //       been reached.
 //   |MOJO_RESULT_BUSY| if |handle| is currently in use in some transaction
 //       (that, e.g., may result in it being invalidated, such as being sent in
 //       a message).
 MojoResult MojoDuplicateHandle(MojoHandle handle,
                                MojoHandle* new_handle);  // Out.
 
 MOJO_END_EXTERN_C
 
 #endif  // MOJO_PUBLIC_C_SYSTEM_HANDLE_H_