Add a new version of the power save blocker class, to be implemented for all platforms.

content/browser/power_save_blocker2.h

+// 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.
+
+#ifndef CONTENT_BROWSER_POWER_SAVE_BLOCKER2_H_
+#define CONTENT_BROWSER_POWER_SAVE_BLOCKER2_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "content/common/content_export.h"
+
+// A RAII-style class to block the system from entering low-power (sleep) mode.
+class CONTENT_EXPORT PowerSaveBlocker2 {
+ public:
+  enum PowerSaveBlockerType {
+    // Prevent the application from being suspended. On some platforms, apps may
+    // be suspended when they are not visible to the user. This type of block
+    // requests that the app continue to run in that case, and on all platforms
+    // prevents the system from sleeping.
+    // Example use cases: downloading a file, playing audio.
+    kPowerSaveBlockPreventAppSuspension,
+
+    // Prevent the display from going to sleep. This also has the side effect of
+    // preventing the system from sleeping, but does not necessarily prevent the
+    // app from being suspended on some platforms if the user hides it.
+    // Example use case: playing video.
+    kPowerSaveBlockPreventDisplaySleep,
+  };
+
+  // Pass in the type of power save blocking desired. If multiple types of
+  // blocking are desired, instantiate one PowerSaveBlocker for each type.
+  explicit PowerSaveBlocker2(PowerSaveBlockerType type);

[Avi (use Gerrit), 2012/06/04 21:58:52]

Can we get a string to describe why?

[Mike Mammarella, 2012/06/04 22:21:28]

Done.

+  ~PowerSaveBlocker2();
+
+ private:
+  class PowerSaveBlockerImpl;
+
+  // Implementations of this class may need a second object with different
+  // lifetime than the RAII container, or additional storage. This member is
+  // here for that purpose.
+  PowerSaveBlockerImpl* impl;

[Avi (use Gerrit), 2012/06/04 21:58:52]

Huh. I was going to go for #ifdef-ed member variables here, but I'm OK with
this.

[Mike Mammarella, 2012/06/04 22:21:28]

We could do that too I suppose. In the Linux version (which I haven't actually
started on yet) I am pretty sure I'll want a refcounted delegate with a
different lifetime to pass in messages to another thread, and that's where all
the real state will be anyway. So I figured it's likely that other
implementations could do that too...

+
+  DISALLOW_COPY_AND_ASSIGN(PowerSaveBlocker2);
+};
+
+#endif  // CONTENT_BROWSER_POWER_SAVE_BLOCKER2_H_