Add Core::ReplaceHandleWithReducedRights().

mojo/edk/system/core.cc

 // Copyright 2013 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.
 
 #include "mojo/edk/system/core.h"
 
 #include <memory>
 #include <utility>
 #include <vector>
 
@@ skipping 168 matching lines @@
                            UserPointer<MojoHandleRights> rights) {
   Handle h;
   MojoResult result = GetHandle(handle, &h);
   if (result != MOJO_RESULT_OK)
     return result;
 
   rights.Put(h.rights);
   return MOJO_RESULT_OK;
 }
 
+MojoResult Core::ReplaceHandleWithReducedRights(
+    MojoHandle handle,
+    MojoHandleRights rights_to_remove,
+    UserPointer<MojoHandle> replacement_handle) {
+  if (handle == MOJO_HANDLE_INVALID)
+    return MOJO_RESULT_INVALID_ARGUMENT;
+
+  MojoHandle replacement_handle_value = MOJO_HANDLE_INVALID;
+  {
+    MutexLocker locker(&handle_table_mutex_);
+    MojoResult result = handle_table_.ReplaceHandleWithReducedRights(
+        handle, rights_to_remove, &replacement_handle_value);
+    if (result != MOJO_RESULT_OK)
+      return result;
+  }
+  DCHECK_NE(replacement_handle_value, MOJO_HANDLE_INVALID);
+
+  replacement_handle.Put(replacement_handle_value);
+  return MOJO_RESULT_OK;
+}
+
 MojoResult Core::DuplicateHandleWithReducedRights(
     MojoHandle handle,
     MojoHandleRights rights_to_remove,
     UserPointer<MojoHandle> new_handle) {
   Handle h;
   MojoResult result = GetHandle(handle, &h);
   if (result != MOJO_RESULT_OK)
     return result;
 
   if (!h.has_all_rights(MOJO_HANDLE_RIGHT_DUPLICATE))
@@ skipping 592 matching lines @@
   if (signals_states) {
     for (; i < num_handles; i++)
       signals_states[i] = dispatchers[i]->GetHandleSignalsState();
   }
 
   return result;
 }
 
 }  // namespace system
 }  // namespace mojo