[Mac] Maximise timer slack for background tabs

base/message_loop/timer_slack.h

Index: base/message_loop/timer_slack.h
diff --git a/base/message_loop/timer_slack.h b/base/message_loop/timer_slack.h
new file mode 100644
index 0000000000000000000000000000000000000000..1ad6ca94a1b719485f29ce07b78af2861e371b19
--- /dev/null
+++ b/base/message_loop/timer_slack.h
@@ -0,0 +1,22 @@
+// Copyright 2014 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.
+
+#ifndef BASE_MESSAGE_LOOP_TIMER_SLACK_H_
+#define BASE_MESSAGE_LOOP_TIMER_SLACK_H_
+
+namespace base {
+
+// Amount of timer slack to use for delayed timers.  Increasing timer slack
+// allows the OS to coalesce timers more effectively.
+enum TimerSlack {
+  // Lowest value for timer slack allowed by OS.
+  TIMER_SLACK_NONE,
+
+  // Maximal value for timer slack allowed by OS.
+  TIMER_SLACK_MAXIMUM
+};
+
+}  // namespace base
+
+#endif  // BASE_MESSAGE_LOOP_TIMER_SLACK_H_