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 36bcc92828cfe99dc7fe286b178266729a9e34d0..158b4469ed31ddacf2ada259a21a59e5310fa6c8 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