mash: make Env::last_mouse_location() accurate for Mus

ui/aura/test/aura_test_base.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 UI_AURA_TEST_AURA_TEST_BASE_H_
 #define UI_AURA_TEST_AURA_TEST_BASE_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 143 matching lines @@
 
   // AuraTestBase:
   void SetUp() override;
 
  private:
   bool setup_called_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(AuraTestBaseWithType);
 };
 
+class AuraTestBaseMus : public AuraTestBase {
+ public:
+  AuraTestBaseMus();
+  ~AuraTestBaseMus() override;
+
+  // AuraTestBase:
+  void SetUp() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AuraTestBaseMus);
+};
+
 }  // namespace test
 }  // namespace aura
 
 #endif  // UI_AURA_TEST_AURA_TEST_BASE_H_