ozone: dri: Fix undefined references in DRI platform GN build

ui/ozone/platform/dri/screen_manager.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_OZONE_PLATFORM_DRI_SCREEN_MANAGER_H_
 #define UI_OZONE_PLATFORM_DRI_SCREEN_MANAGER_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_vector.h"
 #include "base/observer_list.h"
+#include "ui/ozone/ozone_export.h"
 #include "ui/ozone/platform/dri/display_change_observer.h"
 #include "ui/ozone/platform/dri/hardware_display_controller.h"
 
 typedef struct _drmModeModeInfo drmModeModeInfo;
 
 namespace gfx {
 class Point;
 class Rect;
 class Size;
 }  // namespace gfx
 
 namespace ui {
 
 class DriWrapper;
 class ScanoutBufferGenerator;
 
 // Responsible for keeping track of active displays and configuring them.
-class ScreenManager {
+class OZONE_EXPORT ScreenManager {
  public:
   ScreenManager(DriWrapper* dri, ScanoutBufferGenerator* surface_generator);
   virtual ~ScreenManager();
 
   // Register a display controller. This must be called before trying to
   // configure it.
   void AddDisplayController(DriWrapper* dri, uint32_t crtc, uint32_t connector);
 
   // Remove a display controller from the list of active controllers. The
   // controller is removed since it was disconnected.
@@ skipping 54 matching lines @@
   HardwareDisplayControllers controllers_;
 
   ObserverList<DisplayChangeObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenManager);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRI_SCREEN_MANAGER_H_