[ozone] Enable display controller before notifying its users that it's available.

ui/ozone/platform/dri/screen_manager.cc

Index: ui/ozone/platform/dri/screen_manager.cc
diff --git a/ui/ozone/platform/dri/screen_manager.cc b/ui/ozone/platform/dri/screen_manager.cc
index e273bbdd24abc7c4e198e868e490eaf057391337..bb5833b83e5926ad15c3502e0ed0f012fde084fb 100644
--- a/ui/ozone/platform/dri/screen_manager.cc
+++ b/ui/ozone/platform/dri/screen_manager.cc
@@ -121,10 +121,12 @@ bool ScreenManager::ConfigureDisplayController(uint32_t crtc,
         return HandleMirrorMode(it, mirror, crtc, connector);
     }
 
+    // Just re-enable the controller to re-use the current state.
+    bool enabled = controller->Enable();
     FOR_EACH_OBSERVER(DisplayChangeObserver, observers_,
                       OnDisplayChanged(controller));
-    // Just re-enable the controller to re-use the current state.
-    return controller->Enable();
+
+    return enabled;
   }
 
   // Either the mode or the location of the display changed, so exit mirror