[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..df6b37258f7e92d4a36a0cc61ffa5832a6babd20
--- /dev/null
+++ b/base/message_loop/timer_slack.h
@@ -0,0 +1,24 @@
+// 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_
+
+#include "base/base_export.h"
+
+namespace base {
+
+enum TimerSlack {
+  TIMER_SLACK_NONE,
+  TIMER_SLACK_MAXIMUM
+};
+
+// Sets the global timer slack number for this process.

[tonyg, 2014/05/20 14:14:52]

Why is this process wide? I thought that we could get per-thread everywhere and
per-timer some places. So a good starter implementation seems to be per-thread
only (since we can do that everywhere).

Would it be possible to do that on the MessageLoop instance itself instead of as
a global static setting like this? It guarantees a max of one MessageLoop
instance per thread.

+void SetTimerSlack(TimerSlack timer_slack) BASE_EXPORT;
+
+TimerSlack GetTimerSlack();
+
+}  // namespace base
+
+#endif  // BASE_MESSAGE_LOOP_TIMER_SLACK_H_