Add support for backgrounding processes on the Mac

content/browser/child_process_launcher.cc

 // Copyright (c) 2012 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 "content/browser/child_process_launcher.h"
 
 #include <utility>  // For std::pair.
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 485 matching lines @@
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
                 zygote_,
 #endif
                 base::Passed(&process_)));
 }
 
 // static
 void ChildProcessLauncher::Context::SetProcessBackgroundedInternal(
     base::Process process,
     bool background) {
+#if defined(OS_MACOSX)
+  MachBroker* broker = MachBroker::GetInstance();
+  process.SetProcessBackgrounded(broker->TaskForPid(process.Pid()), background);

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

To analyze the impact of this you'll want to put this behind an experiment.

See https://codereview.chromium.org/926663002 for an example of how to set this
up with experiments, you'll probably only care to have two modes (ON/OFF) in
your case.

+#else
   process.SetProcessBackgrounded(background);
+#endif  // defined(OS_MACOSX)
 #if defined(OS_ANDROID)
   SetChildProcessInForeground(process.Handle(), !background);
 #endif
 }
 
 // static
 void ChildProcessLauncher::Context::TerminateInternal(
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
     bool zygote,
 #endif
@@ skipping 78 matching lines @@
   context_->SetProcessBackgrounded(background);
 }
 
 void ChildProcessLauncher::SetTerminateChildOnShutdown(
     bool terminate_on_shutdown) {
   if (context_.get())
     context_->set_terminate_child_on_shutdown(terminate_on_shutdown);
 }
 
 }  // namespace content