Fix use after free for cached_displays_.

ui/display/manager/chromeos/test/test_native_display_delegate.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_DISPLAY_MANAGER_CHROMEOS_TEST_TEST_NATIVE_DISPLAY_DELEGATE_H_
 #define UI_DISPLAY_MANAGER_CHROMEOS_TEST_TEST_NATIVE_DISPLAY_DELEGATE_H_
 
 #include <stdint.h>
 
 #include <vector>
 
 #include "base/macros.h"
+#include "base/observer_list.h"
 #include "ui/display/manager/chromeos/test/action_logger.h"
 #include "ui/display/manager/chromeos/test/action_logger_util.h"
 #include "ui/display/types/native_display_delegate.h"
 
 namespace ui {
 
 class ActionLogger;
 class DisplaySnapshot;
+class NativeDisplayObserver;
 
 namespace test {
 
 class TestNativeDisplayDelegate : public NativeDisplayDelegate {
  public:
   // Ownership of |log| remains with the caller.
   explicit TestNativeDisplayDelegate(ActionLogger* log);
   ~TestNativeDisplayDelegate() override;
 
   const std::vector<DisplaySnapshot*>& outputs() const { return outputs_; }
@@ skipping 73 matching lines @@
   bool set_hdcp_expectation_;
 
   // Result value of GetHDCPState().
   HDCPState hdcp_state_;
 
   // If true, the callbacks are posted on the message loop.
   bool run_async_;
 
   ActionLogger* log_;  // Not owned.
 
+  base::ObserverList<NativeDisplayObserver> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(TestNativeDisplayDelegate);
 };
 
 }  // namespace test
 }  // namespace ui
 
 #endif  // UI_DISPLAY_MANAGER_CHROMEOS_TEST_TEST_NATIVE_DISPLAY_DELEGATE_H_