[Refactor] Consolidate the logic for whether a widget can be activated.

ash/wm/overview/window_overview.cc

Index: ash/wm/overview/window_overview.cc
diff --git a/ash/wm/overview/window_overview.cc b/ash/wm/overview/window_overview.cc
index f84d633f57a5b704e3bddd8a8b2a135c67b254c3..71785aea8ad8e239ed7c6a4dff9248967e38351e 100644
--- a/ash/wm/overview/window_overview.cc
+++ b/ash/wm/overview/window_overview.cc
@@ -427,7 +427,6 @@ void WindowOverview::InitializeSelectionWidget() {
   selection_widget_.reset(new views::Widget);
   views::Widget::InitParams params;
   params.type = views::Widget::InitParams::TYPE_POPUP;
-  params.can_activate = false;
   params.keep_on_top = false;
   params.ownership = views::Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
   params.opacity = views::Widget::InitParams::OPAQUE_WINDOW;