Revert of Add support for backgrounding processes on the Mac

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 2b65381328cb8cd201a87005c1ae4def59cbbea9..14006ce388f2c59fd6e83ec6256919e5f01b3bba 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1,4 +1,4 @@
-// Copyright 2012 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -2216,15 +2216,14 @@
     return;
 #endif  // OS_WIN
 
-#if defined(OS_WIN) || defined(OS_MACOSX)
-  // Same as below, but bound to an experiment (http://crbug.com/458594 on
-  // Windows, http://crbug.com/398103 on the Mac). Enabled by default in the
-  // absence of field trials to get coverage on the perf waterfall.
+#if defined(OS_WIN)
+  // Same as below, but bound to an experiment (http://crbug.com/458594)
+  // initially on Windows. Enabled by default in the asbence of field trials to
+  // get coverage on the perf waterfall.
   base::FieldTrial* trial =
       base::FieldTrialList::Find("BackgroundRendererProcesses");
-  if (!trial || !StartsWithASCII(trial->group_name(), "Disallow", true)) {
+  if (!trial || trial->group_name() != "Disallow")
     child_process_launcher_->SetProcessBackgrounded(backgrounded);
-  }
 #else
   // Control the background state from the browser process, otherwise the task
   // telling the renderer to "unbackground" itself may be preempted by other