aura-mus: Implement Deactivate().

ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
index cfc4f0d6f8c37cf2da4e63a17ef5495930eb79f1..3b848bc9ddb9aa899dc8eaf96f30a0a97998e5b1 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
@@ -482,6 +482,8 @@ void DesktopWindowTreeHostX11::OnNativeWidgetCreated(
 
 void DesktopWindowTreeHostX11::OnWidgetInitDone() {}
 
+void DesktopWindowTreeHostX11::OnNativeWidgetActivationChanged(bool active) {}
+
 std::unique_ptr<corewm::Tooltip> DesktopWindowTreeHostX11::CreateTooltip() {
   return base::WrapUnique(new corewm::TooltipAura);
 }