Adds ability for ash_unittests to run in mushrome mode

ash/test/ash_test_suite.h

 // Copyright (c) 2012 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_TEST_SUITE_H_
 #define ASH_TEST_ASH_TEST_SUITE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/test/test_discardable_memory_allocator.h"
 #include "base/test/test_suite.h"
 #include "ui/aura/env.h"
 
+namespace ui {
+class FakeContextFactory;
+}
+
 namespace ash {
 namespace test {
 
 class AshTestSuite : public base::TestSuite {
  public:
   AshTestSuite(int argc, char** argv);
   ~AshTestSuite() override;
 
  protected:
   // base::TestSuite:
   void Initialize() override;
   void Shutdown() override;
 
  private:
   std::unique_ptr<aura::Env> env_;
 
   base::TestDiscardableMemoryAllocator discardable_memory_allocator_;
 
+  // Only used when running in Config::MUS, and is set as the context_factory
+  // on aura::Env.
+  std::unique_ptr<ui::FakeContextFactory> context_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(AshTestSuite);
 };
 
 }  // namespace test
 }  // namespace ash
 
 #endif  // ASH_TEST_ASH_TEST_SUITE_H_