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

ui/aura/test/env_test_helper.h

 // 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.
 
 #ifndef UI_AURA_TEST_ENV_TEST_HELPER_H_
 #define UI_AURA_TEST_ENV_TEST_HELPER_H_
 
 #include <utility>
 
 #include "base/macros.h"
@@ skipping 20 matching lines @@
   }
 
   void SetMode(Env::Mode mode) { env_->mode_ = mode; }
 
   // This circumvents the DCHECKs in Env::SetWindowTreeClient() and should
   // only be used for tests where Env is long lived.
   void SetWindowTreeClient(WindowTreeClient* window_tree_client) {
     env_->window_tree_client_ = window_tree_client;
   }
 
+  void SetAlwaysUseLastMouseLocation(bool value) {
+    env_->always_use_last_mouse_location_ = value;
+  }
+
  private:
   Env* env_;
 
   DISALLOW_COPY_AND_ASSIGN(EnvTestHelper);
 };
 
 }  // namespace test
 }  // namespace aura
 
 #endif  // UI_AURA_TEST_ENV_TEST_HELPER_H_