Updates the display message in the uber tray.

ash/drag_drop/drag_drop_tracker_unittest.cc

Index: ash/drag_drop/drag_drop_tracker_unittest.cc
diff --git a/ash/drag_drop/drag_drop_tracker_unittest.cc b/ash/drag_drop/drag_drop_tracker_unittest.cc
index acb87a46a54b78db87ea7a0f09314a9a6d125823..081b04bc2bbb45ca2a27e8a6514bca9b0e8ad214 100644
--- a/ash/drag_drop/drag_drop_tracker_unittest.cc
+++ b/ash/drag_drop/drag_drop_tracker_unittest.cc
@@ -4,8 +4,10 @@
 
 #include "ash/drag_drop/drag_drop_tracker.h"
 
+#include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
+#include "ash/system/tray/system_tray.h"
 #include "ash/test/ash_test_base.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/aura/root_window.h"
@@ -20,6 +22,14 @@ class DragDropTrackerTest : public test::AshTestBase {
   virtual void SetUp() OVERRIDE {
     AshTestBase::SetUp();
     UpdateDisplay("200x200,200x200");
+    // close all notification for display change. Otherwise some event may
+    // happen on the notification bubble, which breaks the test expectation.
+    // TODO(mukai): remove this when the display change notification has moved
+    // to the message_center.
+    Shell::RootWindowControllerList root_controllers =
+        Shell::GetAllRootWindowControllers();
+    for (size_t i = 0; i < root_controllers.size(); ++i)
+      root_controllers[i]->GetSystemTray()->CloseNotificationBubbleForTest();
   }
 
   aura::Window* CreateTestWindow(const gfx::Rect& bounds) {