Hidden windows should not keep Chrome alive.

extensions/browser/app_window/app_delegate.h

Index: extensions/browser/app_window/app_delegate.h
diff --git a/extensions/browser/app_window/app_delegate.h b/extensions/browser/app_window/app_delegate.h
index 70f9f1228cd9dcd79374d05a9f80488f229f7c8b..278e09407875294af593b6d0c9b91c2d552decd2 100644
--- a/extensions/browser/app_window/app_delegate.h
+++ b/extensions/browser/app_window/app_delegate.h
@@ -78,6 +78,10 @@ class AppDelegate {
 
   // |callback| will be called when the process is about to terminate.
   virtual void SetTerminatingCallback(const base::Closure& callback) = 0;
+
+  // Called when the app is hidden or shown.
+  virtual void OnHide() = 0;
+  virtual void OnShow() = 0;
 };
 
 }  // namespace extensions