Fix prctl ERROR messages on Linux debug builds.

base/threading/platform_thread_posix.cc

 // Copyright (c) 2011 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 "base/threading/platform_thread.h"
 
 #include <errno.h>
 #include <sched.h>
 
 #include "base/lazy_instance.h"
@@ skipping 172 matching lines @@
   // On linux we can get the thread names to show up in the debugger by setting
   // the process name for the LWP.  We don't want to do this for the main
   // thread because that would rename the process, causing tools like killall
   // to stop working.
   if (PlatformThread::CurrentId() == getpid())
     return;
 
   // http://0pointer.de/blog/projects/name-your-threads.html
   // Set the name for the LWP (which gets truncated to 15 characters).
   // Note that glibc also has a 'pthread_setname_np' api, but it may not be
-  // available everywhere and doesn't seem to have any advantage over using
-  // prctl.
+  // available everywhere and it's only benefit over using prctl directly is
+  // that it can set the name of threads other than the current thread.
   int err = prctl(PR_SET_NAME, name);
-  if (err < 0)
+  // We expect EPERM failures in sandboxed processes, just ignore those.
+  if (err < 0 && errno != EPERM)
     DPLOG(ERROR) << "prctl(PR_SET_NAME)";
 }
 #elif defined(OS_MACOSX)
 // Mac is implemented in platform_thread_mac.mm.
 #else
 // static
 void PlatformThread::SetName(const char* name) {
   // have to cast away const because ThreadLocalPointer does not support const
   // void*
   current_thread_name.Pointer()->Set(const_cast<char*>(name));
@@ skipping 42 matching lines @@
 // Mac OS X uses lower-level mach APIs
 
 // static
 void PlatformThread::SetThreadPriority(PlatformThreadHandle, ThreadPriority) {
   // TODO(crogers): implement
   NOTIMPLEMENTED();
 }
 #endif
 
 }  // namespace base