Fix Volume slider is captured in screenshot done in touchview mode

ash/wm/power_button_controller.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_WM_POWER_BUTTON_CONTROLLER_H_
 #define ASH_WM_POWER_BUTTON_CONTROLLER_H_
 
 #include "ash/ash_export.h"
 #include "base/macros.h"
 #include "base/time/time.h"
@@ skipping 69 matching lines @@
  private:
   friend class test::PowerButtonControllerTest;
 
   // Are the power or lock buttons currently held?
   bool power_button_down_;
   bool lock_button_down_;
 
   // True when the volume down button is being held down.
   bool volume_down_pressed_;
 
+#if defined(OS_CHROMEOS)
+  // Volume to be restored after a screenshot is taken by pressing the power
+  // button while holding VKEY_VOLUME_DOWN.
+  int volume_percent_before_screenshot_;
+#endif
+
   // Has the screen brightness been reduced to 0%?
   bool brightness_is_zero_;
 
   // True if an internal display is off while an external display is on (e.g.
   // for Chrome OS's docked mode, where a Chromebook's lid is closed while an
   // external display is connected).
   bool internal_display_off_and_external_display_on_;
 
   // Was a command-line switch set telling us that we're running on hardware
   // that misreports power button releases?
   bool has_legacy_power_button_;
 
   // Enables quick, non-cancellable locking of the screen when in maximize mode.
   bool enable_quick_lock_;
 
   LockStateController* controller_;  // Not owned.
 
   DISALLOW_COPY_AND_ASSIGN(PowerButtonController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_POWER_BUTTON_CONTROLLER_H_