Fix Volume slider is captured in screenshot done in touchview mode

ash/wm/power_button_controller.h

Index: ash/wm/power_button_controller.h
diff --git a/ash/wm/power_button_controller.h b/ash/wm/power_button_controller.h
index 970ddab86dc8ce1bec159fa736c39dad267c7513..4364da72dbfa966211d5e13af7e426b9706016d1 100644
--- a/ash/wm/power_button_controller.h
+++ b/ash/wm/power_button_controller.h
@@ -87,6 +87,11 @@ class ASH_EXPORT PowerButtonController
   // True when the volume down button is being held down.
   bool volume_down_pressed_;
 
+#if defined(OS_CHROMEOS)
+  // Volume to be restored after a maximize mode screenshot.
+  int volume_percent_before_screenshot_;
+#endif
+
   // Has the screen brightness been reduced to 0%?
   bool brightness_is_zero_;