Hide notifications popups when entering fullscreen mode.

ui/message_center/message_center_tray_unittest.cc

Index: ui/message_center/message_center_tray_unittest.cc
diff --git a/ui/message_center/message_center_tray_unittest.cc b/ui/message_center/message_center_tray_unittest.cc
index bf2005b25418ea124a44b15ce29622b095a23415..108cee7aa29ed5d9c1e5db5614a5f09c2cdc5cc7 100644
--- a/ui/message_center/message_center_tray_unittest.cc
+++ b/ui/message_center/message_center_tray_unittest.cc
@@ -31,6 +31,10 @@ class MockDelegate : public MessageCenterTrayDelegate {
     return false;
   }
 
+  virtual MessageCenterTray* GetMessageCenterTray() OVERRIDE {
+    return NULL;
+  }
+
   bool show_popups_success_;
   bool show_message_center_success_;