Fix X11DesktopHandler::ActivateWindow on Unity for known user gestures

ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
index 94d4b1ba2f2a480ba90bcf89f8f77d58a0114d7f..e37a3ff13668d5301bc49b92870eefcaef62d522 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
@@ -111,6 +111,7 @@ class VIEWS_EXPORT DesktopWindowTreeHostX11
   gfx::Rect GetWorkAreaBoundsInScreen() const override;
   void SetShape(gfx::NativeRegion native_region) override;
   void Activate() override;
+  void ActivateForUserGesture() override;
   void Deactivate() override;
   bool IsActive() const override;
   void Maximize() override;