linux: fix race in TransportDIB passing

chrome/common/transport_dib_linux.cc

 // Copyright (c) 2009 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 <errno.h>
 #include <stdlib.h>
 #include <sys/ipc.h>
 #include <sys/shm.h>
 
 #include "base/gfx/size.h"
@@ skipping 27 matching lines @@
 
 // static
 TransportDIB* TransportDIB::Create(size_t size, uint32 sequence_num) {
   // We use a mode of 0666 since the X server won't attach to memory which is
   // 0600 since it can't know if it (as a root process) is being asked to map
   // someone else's private shared memory region.
   const int shmkey = shmget(IPC_PRIVATE, size, 0666);
   if (shmkey == -1) {
     DLOG(ERROR) << "Failed to create SysV shared memory region"
                 << " errno:" << errno;
-    return false;
+    return NULL;
   }
 
   void* address = shmat(shmkey, NULL /* desired address */, 0 /* flags */);
   // Here we mark the shared memory for deletion. Since we attached it in the
   // line above, it doesn't actually get deleted but, if we crash, this means
   // that the kernel will automatically clean it up for us.
   shmctl(shmkey, IPC_RMID, 0);
   if (address == kInvalidAddress)
-    return false;
+    return NULL;
 
   TransportDIB* dib = new TransportDIB;
 
   dib->key_ = shmkey;
   dib->address_ = address;
   dib->size_ = size;
   return dib;
 }
 
 TransportDIB* TransportDIB::Map(Handle shmkey) {
@@ skipping 36 matching lines @@
 }
 
 XID TransportDIB::MapToX(Display* display) {
   if (!x_shm_) {
     x_shm_ = x11_util::AttachSharedMemory(display, key_);
     display_ = display;
   }
 
   return x_shm_;
 }