Add unit tests for screen capture and share notification UI.

ash/system/chromeos/screen_security/screen_capture_tray_item.h

Index: ash/system/chromeos/screen_security/screen_capture_tray_item.h
diff --git a/ash/system/chromeos/screen_security/screen_capture_tray_item.h b/ash/system/chromeos/screen_security/screen_capture_tray_item.h
index a7564169bcaa55c0d43317bdf061f68fd6ec75ad..f1fb4b5295eb4edaad6b5bf2848fcf7b5ed64fd6 100644
--- a/ash/system/chromeos/screen_security/screen_capture_tray_item.h
+++ b/ash/system/chromeos/screen_security/screen_capture_tray_item.h
@@ -15,8 +15,8 @@ class View;
 namespace ash {
 namespace internal {
 
-class ScreenCaptureTrayItem : public ScreenTrayItem,
-                              public ScreenCaptureObserver {
+class ASH_EXPORT ScreenCaptureTrayItem : public ScreenTrayItem,
+                                         public ScreenCaptureObserver {
  public:
   explicit ScreenCaptureTrayItem(SystemTray* system_tray);
   virtual ~ScreenCaptureTrayItem();