Specify a default display UI scale to reset the zoom to

ash/test/display_manager_test_api.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_DISPLAY_MANAGER_TEST_API_H_
 #define ASH_TEST_DISPLAY_MANAGER_TEST_API_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 44 matching lines @@
 
   // Sets the available color profiles for |display_id|.
   void SetAvailableColorProfiles(
       int64_t display_id,
       const std::vector<ui::ColorCalibrationProfile>& profiles);
 
   // Gets the internal display::ManagedDisplayInfo for a specific display id.
   const display::ManagedDisplayInfo& GetInternalManagedDisplayInfo(
       int64_t display_id);
 
+  // Sets the UI scale for the |display_id|. Returns false if the
+  // display_id is not an internal display.
+  bool SetDisplayUIScale(int64_t display_id, float scale);
+
  private:
   friend class ScopedSetInternalDisplayId;
   // Sets the display id for internal display and
   // update the display mode list if necessary.
   void SetInternalDisplayId(int64_t id);
 
   DisplayManager* display_manager_;  // not owned
 
   DISALLOW_COPY_AND_ASSIGN(DisplayManagerTestApi);
 };
@@ skipping 32 matching lines @@
     int offset);
 
 // Creates the DisplayIdList from ints.
 display::DisplayIdList CreateDisplayIdList2(int64_t id1, int64_t id2);
 display::DisplayIdList CreateDisplayIdListN(size_t count, ...);
 
 }  // namespace test
 }  // namespace ash
 
 #endif  // ASH_TEST_DISPLAY_MANAGER_TEST_API_H_