Fix "modal isn't modal in multi displays" issue

ash/wm/system_modal_container_layout_manager.cc

Index: ash/wm/system_modal_container_layout_manager.cc
diff --git a/ash/wm/system_modal_container_layout_manager.cc b/ash/wm/system_modal_container_layout_manager.cc
index 8a9e859fcc8f14e3904415e4fc7988e384613f12..8d031339de6d95e781ea96f62f39db814fb9aab2 100644
--- a/ash/wm/system_modal_container_layout_manager.cc
+++ b/ash/wm/system_modal_container_layout_manager.cc
@@ -113,22 +113,9 @@ void SystemModalContainerLayoutManager::OnKeyboardBoundsChanging(
   PositionDialogsAfterWorkAreaResize();
 }
 
-bool SystemModalContainerLayoutManager::CanWindowReceiveEvents(
+bool SystemModalContainerLayoutManager::IsActiveModalWindows(
     aura::Window* window) {
-  // We could get when we're at lock screen and there is modal window at
-  // system modal window layer which added event filter.
-  // Now this lock modal windows layer layout manager should not block events
-  // for windows at lock layer.
-  // See SystemModalContainerLayoutManagerTest.EventFocusContainers and
-  // http://crbug.com/157469
-  if (modal_windows_.empty())
-    return true;
-  // This container can not handle events if the screen is locked and it is not
-  // above the lock screen layer (crbug.com/110920).
-  if (Shell::GetInstance()->session_state_delegate()->IsUserSessionBlocked() &&
-      container_->id() < ash::kShellWindowId_LockScreenContainer)
-    return true;
-  return wm::GetActivatableWindow(window) == modal_window();
+  return modal_window() && wm::GetActivatableWindow(window) == modal_window();
 }
 
 bool SystemModalContainerLayoutManager::ActivateNextModalWindow() {