Add support for backgrounding processes on the Mac

content/browser/child_process_launcher.cc

Index: content/browser/child_process_launcher.cc
diff --git a/content/browser/child_process_launcher.cc b/content/browser/child_process_launcher.cc
index e5c93ee3562bbecd378d96c671d77c4fe219c39e..c5a09cace656451d0da412ebccccc81b8d2d9e2c 100644
--- a/content/browser/child_process_launcher.cc
+++ b/content/browser/child_process_launcher.cc
@@ -503,7 +503,12 @@ void ChildProcessLauncher::Context::Terminate() {
 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