Introduce 'grab_inputs' property for athena container.

athena/home/home_card_impl.cc

Index: athena/home/home_card_impl.cc
diff --git a/athena/home/home_card_impl.cc b/athena/home/home_card_impl.cc
index df3b0f60e1459d01810c5e4abde98ce97bdd1ffd..9a714144195f73a1c4abd26d85e296614ef7cd14 100644
--- a/athena/home/home_card_impl.cc
+++ b/athena/home/home_card_impl.cc
@@ -241,8 +241,10 @@ class HomeCardImpl : public HomeCard,
   // aura::client::ActivationChangeObserver:
   virtual void OnWindowActivated(aura::Window* gained_active,
                                  aura::Window* lost_active) OVERRIDE {
-    if (gained_active != home_card_widget_->GetNativeWindow())
+    if (state_ != HIDDEN &&
+        gained_active != home_card_widget_->GetNativeWindow()) {
       SetState(VISIBLE_MINIMIZED);
+    }
   }
 
   scoped_ptr<AppModelBuilder> model_builder_;