Clean up selected ash defines for MessagePumpLinux

ash/wm/system_gesture_event_filter.cc

Index: ash/wm/system_gesture_event_filter.cc
diff --git a/ash/wm/system_gesture_event_filter.cc b/ash/wm/system_gesture_event_filter.cc
index 6810eaeb54b4b3934a1d9b7410b3d265c1389186..027d048118205a1d353828fc0f9871158b71be63 100644
--- a/ash/wm/system_gesture_event_filter.cc
+++ b/ash/wm/system_gesture_event_filter.cc
@@ -56,7 +56,8 @@ SystemGestureEventFilter::~SystemGestureEventFilter() {
 }
 
 void SystemGestureEventFilter::OnMouseEvent(ui::MouseEvent* event) {
-#if defined(OS_CHROMEOS)
+// TODO(rjkroege): Remove USE_MESSAGEPUMP_LINUX guard once mice are supported.
+#if defined(OS_CHROMEOS) && !defined(USE_MESSAGEPUMP_LINUX)
   if (event->type() == ui::ET_MOUSE_PRESSED && event->native_event() &&
       ui::TouchFactory::GetInstance()->IsTouchDevicePresent() &&
       Shell::GetInstance()->delegate()) {