[Mac] Enable AppNap for renderers

content/common/mac/app_nap_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_APP_NAP_ACTIVITY_H
 #define CONTENT_COMMON_MAC_APP_NAP_ACTIVITY_H
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/common/content_export.h"
 
 namespace content {
 
 // Can't import scoped_nsobject here, so wrap it.
 struct 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 AppNapActivity {
  public:
   AppNapActivity();
   ~AppNapActivity();
 
+  // Because there's no NSApplication in renderers, do some housekeeping
+  // to become eligible for App Nap.
+  static void InitializeAppNapSupport();
+
   // Begin an activity and store the provided token.
   void Begin();
 
   // End the activity represented by |assertion_|.
   void End();
 
  private:
   // An opaque token provided by the OS on beginning an activity.
   std::unique_ptr<AssertionWrapper> assertion_;
 
   DISALLOW_COPY_AND_ASSIGN(AppNapActivity);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_MAC_APP_NAP_ACTIVITY_H