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"
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/process/process.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/thread.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/common/content_descriptors.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/result_codes.h"
 #include "content/public/common/sandboxed_process_launcher_delegate.h"
@@ skipping 471 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)
+  std::string trialGroupName =

[gab, 2015/03/12 15:50:09]

nit: const

[Alexei Svitkine (slow), 2015/03/12 15:57:07]

hacker_style

[shrike, 2015/03/18 16:20:22]

Done and done.

+      base::FieldTrialList::FindFullName("BackgroundMacRendererProcesses");
+  // Activate backgrounding when the user is part of the field trial, or
+  // there's no trial (i.e. a perf bot)
+  if (trialGroupName != "Off") {
+    MachBroker* broker = MachBroker::GetInstance();
+    process.SetProcessBackgrounded(broker->TaskForPid(process.Pid()),
+                                   background);
+  }
+#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