Show message to indicate that mirriring with more than 3 display is not supported.

ash/display/display_error_observer_chromeos_unittest.cc

 // Copyright 2013 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.
 
 #include "ash/display/display_error_observer_chromeos.h"
 
+#include "ash/display/display_util.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "grit/ash_strings.h"
 #include "ui/aura/window.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
 
 class DisplayErrorObserverTest : public test::AshTestBase {
  protected:
   DisplayErrorObserverTest() {
   }
 
   ~DisplayErrorObserverTest() override {}
 
   void SetUp() override {
     test::AshTestBase::SetUp();
     observer_.reset(new DisplayErrorObserver());
   }
 
  protected:
   DisplayErrorObserver* observer() { return observer_.get(); }
 
   base::string16 GetMessageContents() {
-    return observer_->GetDisplayErrorNotificationMessageForTest();
+    return GetDisplayErrorNotificationMessageForTest();
   }
 
  private:
   std::unique_ptr<DisplayErrorObserver> observer_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayErrorObserverTest);
 };
 
 TEST_F(DisplayErrorObserverTest, Normal) {
   if (!SupportsMultipleDisplays())
@@ skipping 38 matching lines @@
             GetMessageContents());
 
   observer()->OnDisplayModeChangeFailed(
       ui::DisplayConfigurator::DisplayStateList(),
       ui::MULTIPLE_DISPLAY_STATE_DUAL_EXTENDED);
   EXPECT_EQ(l10n_util::GetStringUTF16(IDS_ASH_DISPLAY_FAILURE_ON_NON_MIRRORING),
             GetMessageContents());
 }
 
 }  // namespace ash