[Mac] Enable AppNap for renderers

content/child/child_thread_impl.h

Index: content/child/child_thread_impl.h
diff --git a/content/child/child_thread_impl.h b/content/child/child_thread_impl.h
index a7e2cd2f2565f7f504b80f0de81c1d219a6d3d93..ab9a4ecc8259598751fe270a4acb3cacf4d600c0 100644
--- a/content/child/child_thread_impl.h
+++ b/content/child/child_thread_impl.h
@@ -59,6 +59,10 @@ class QuotaMessageFilter;
 class ResourceDispatcher;
 class ThreadSafeSender;
 
+#if defined(OS_MACOSX)
+class AppNapActivity;
+#endif
+
 // The main thread of a child process derives from this class.
 class CONTENT_EXPORT ChildThreadImpl
     : public IPC::Listener,
@@ -281,6 +285,10 @@ class CONTENT_EXPORT ChildThreadImpl
 
   scoped_refptr<base::SingleThreadTaskRunner> browser_process_io_runner_;
 
+#if defined(OS_MACOSX)
+  std::unique_ptr<AppNapActivity> app_nap_activity_;
+#endif  // defined(OS_MACOSX)
+
   std::unique_ptr<base::WeakPtrFactory<ChildThreadImpl>>
       channel_connected_factory_;