Add support for backgrounding processes on the Mac

base/process/process_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/process/process.h"
 
 #include <sys/resource.h>
 #include <sys/wait.h>
 
 #include "base/files/scoped_file.h"
@@ skipping 231 matching lines @@
   // On POSIX there are no privileges to set.
   return Open(pid);
 }
 
 // static
 Process Process::DeprecatedGetProcessFromHandle(ProcessHandle handle) {
   DCHECK_NE(handle, GetCurrentProcessHandle());
   return Process(handle);
 }
 
-#if !defined(OS_LINUX)
+#if !defined(OS_LINUX) && !defined(OS_MACOSX)
 // static
 bool Process::CanBackgroundProcesses() {
   return false;
 }
-#endif  // !defined(OS_LINUX)
+#endif  // !defined(OS_LINUX) && !defined(OS_MACOSX)
 
 bool Process::IsValid() const {
   return process_ != kNullProcessHandle;
 }
 
 ProcessHandle Process::Handle() const {
   return process_;
 }
 
 Process Process::Duplicate() const {
@@ skipping 28 matching lines @@
 }
 
 bool Process::WaitForExit(int* exit_code) {
   return WaitForExitWithTimeout(TimeDelta::Max(), exit_code);
 }
 
 bool Process::WaitForExitWithTimeout(TimeDelta timeout, int* exit_code) {
   return WaitForExitWithTimeoutImpl(Handle(), exit_code, timeout);
 }
 
-#if !defined(OS_LINUX)
+#if !defined(OS_LINUX) && !defined(OS_MACOSX)
 bool Process::IsProcessBackgrounded() const {
   // See SetProcessBackgrounded().
   DCHECK(IsValid());
   return false;
 }
 
 bool Process::SetProcessBackgrounded(bool value) {
   // 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.

[gab, 2015/03/09 15:34:50]

Update this comment? i.e. we do it on Linux, Chrome OS, and now Mac so this
comment doesn't really make sense.

(also consider adding a NOTIMPLEMENTED() macro to make it explicit that this
could be enabled on other POSIX platforms, just isn't)

[shrike, 2015/03/10 00:34:44]

I added NOTIMPLEMENTED() to this method, but the unit test includes the
following comment:

// Note: a platform may not be willing or able to lower the priority of
// a process. The calls to SetProcessBackground should be noops then.

Is it the case that whenever the unit test runs on a platform that hits the
NOTIMPLEMENTED() call, the unit test will fail?

[gab, 2015/03/10 12:29:35]

No, NOTIMPLEMENTED() simply results in an ERROR LOG [1] and is common practice
[2] for cross-platform calls that are lacking an implementation on a given
platform.

i.e., yes, it's still a no-op implementation.

The NOTIMPLEMENTED() macro serves both as a runtime hint that unimplemented
paths are being hit when debugging and as an explicit code hint for things that
are not intended to work a given way but are rather a default implementation
pending a real one.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/base/logging.h&q=N...

[2]
https://code.google.com/p/chromium/codesearch#search/&q=NOTIMPLEMENTED%5C(%5C...

   DCHECK(IsValid());
   return false;
 }
-#endif  // !defined(OS_LINUX)
+#endif  // !defined(OS_LINUX) && !defined(OS_MACOSX)
 
 int Process::GetPriority() const {
   DCHECK(IsValid());
   return getpriority(PRIO_PROCESS, process_);
 }
 
-}  // namspace base
+}  // namespace base