aura: Require explicit ownership of the Env instance.

ash/test/ash_interactive_ui_test_base.h

 // Copyright 2015 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 ASH_TEST_ASH_INTERACTIVE_UI_TEST_BASE_H_
 #define ASH_TEST_ASH_INTERACTIVE_UI_TEST_BASE_H_
 
+#include <memory>
 #include <string>
 
 #include "ash/test/ash_test_base.h"
 #include "base/macros.h"
 
+namespace aura {
+class Env;
+}
+
 namespace ash {
 namespace test {
 
 class AshInteractiveUITestBase : public AshTestBase {
  public:
   AshInteractiveUITestBase();
   ~AshInteractiveUITestBase() override;
 
  protected:
   // testing::Test:
   void SetUp() override;
   void TearDown() override;
 
  private:
+  std::unique_ptr<aura::Env> env_;
   DISALLOW_COPY_AND_ASSIGN(AshInteractiveUITestBase);
 };
 
 }  // namespace test
 }  // namespace ash
 
 #endif  // ASH_TEST_ASH_INTERACTIVE_UI_TEST_BASE_H_