Revert of Add support for backgrounding processes on the Mac

base/process/process_posix.cc

Index: base/process/process_posix.cc
diff --git a/base/process/process_posix.cc b/base/process/process_posix.cc
index 8037da3ac6e1e09011e581a1ca239023a8b220d2..a7d16f87304f2b38953c9ca9fe42f47e6c0c7634 100644
--- a/base/process/process_posix.cc
+++ b/base/process/process_posix.cc
@@ -1,4 +1,4 @@
-// Copyright 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -253,12 +253,12 @@
   return Process(handle);
 }
 
-#if !defined(OS_LINUX) && !defined(OS_MACOSX)
+#if !defined(OS_LINUX)
 // static
 bool Process::CanBackgroundProcesses() {
   return false;
 }
-#endif  // !defined(OS_LINUX) && !defined(OS_MACOSX)
+#endif  // !defined(OS_LINUX)
 
 bool Process::IsValid() const {
   return process_ != kNullProcessHandle;
@@ -353,7 +353,7 @@
   return WaitForExitWithTimeoutImpl(Handle(), exit_code, timeout);
 }
 
-#if !defined(OS_LINUX) && !defined(OS_MACOSX)
+#if !defined(OS_LINUX)
 bool Process::IsProcessBackgrounded() const {
   // See SetProcessBackgrounded().
   DCHECK(IsValid());
@@ -361,13 +361,13 @@
 }
 
 bool Process::SetProcessBackgrounded(bool value) {
-  // Not implemented for POSIX systems other than Mac and Linux. With POSIX, if
-  // we were to lower the process priority we wouldn't be able to raise it back
-  // to its initial priority.
-  NOTIMPLEMENTED();
+  // POSIX only allows lowering the priority of a process, so if we
+  // were to lower it we wouldn't be able to raise it back to its initial
+  // priority.
+  DCHECK(IsValid());
   return false;
 }
-#endif  // !defined(OS_LINUX) && !defined(OS_MACOSX)
+#endif  // !defined(OS_LINUX)
 
 int Process::GetPriority() const {
   DCHECK(IsValid());