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..d1be6905510383ab3d9fea638059084aaffbf03a 100644
--- a/ash/wm/power_button_controller.h
+++ b/ash/wm/power_button_controller.h
@@ -80,6 +80,8 @@ class ASH_EXPORT PowerButtonController
  private:
   friend class test::PowerButtonControllerTest;
 
+  void TakingScreenshot();
+
   // Are the power or lock buttons currently held?
   bool power_button_down_;
   bool lock_button_down_;
@@ -87,6 +89,12 @@ class ASH_EXPORT PowerButtonController
   // True when the volume down button is being held down.
   bool volume_down_pressed_;
 
+  // Saved everytime the first volume-down is pressed.
+  int first_pressed_volume_percent_;
+
+  // Used to check if this volume-down is the first.
+  bool volume_down_first_;
+
   // Has the screen brightness been reduced to 0%?
   bool brightness_is_zero_;