[Mac] Wrap NSUserActivity begin/end so that it can be called from common files

content/common/mac/activity.h

+// Copyright 2017 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_COMMON_MAC_ACTIVITY_H
+#define CONTENT_COMMON_MAC_ACTIVITY_H
+
+#include <memory>
+
+#include "base/macros.h"
+#include "content/common/content_export.h"
+
+namespace mac {

[Robert Sesek, 2017/05/31 18:11:26]

nit: blank lines surrounding the inside of the namespace declaration

[Robert Sesek, 2017/05/31 18:11:26]

use |namespace content|

[lgrey, 2017/05/31 21:28:11]

Done.

[lgrey, 2017/05/31 21:28:11]

Done.

+// Can't import scoped_nsobject here, so wrap it.
+class AssertionWrapper;
+
+// A wrapper around the macOS "activity" system, which is required to
+// make renderers eligible for AppNap.
+//
+// When doing work, processes are expected to begin an activity, receiving
+// an opaque token called an "assertion". On finishing, they end the activity.
+// When a process has no outstanding assertions, it becomes eligible for
+// AppNap.
+class CONTENT_EXPORT Activity {

[Robert Sesek, 2017/05/31 18:11:26]

"Activity" is a bit broad of a name. What about "AppNapAssertion" or
"AppNapActivity" ?

[lgrey, 2017/05/31 21:28:12]

Done.

+ public:
+  Activity();
+  // Begin an activity and store the provided token.
+  void Begin();

[Robert Sesek, 2017/05/31 18:11:26]

nit: blank line after

[lgrey, 2017/05/31 21:28:11]

Done.

+  // End the activity represented by |assertion_|.
+  void End();
+  ~Activity();

[Robert Sesek, 2017/05/31 18:11:26]

Put this after the ctor.

[lgrey, 2017/05/31 21:28:12]

Done.

+
+ private:
+  // An opaque token provided by the OS on beginning an activity.
+  std::unique_ptr<AssertionWrapper> assertion_;
+
+  DISALLOW_COPY_AND_ASSIGN(Activity);
+};
+}  // namespace mac
+
+#endif  // CONTENT_COMMON_MAC_ACTIVITY_H