Fix Volume slider is captured in screenshot done in touchview mode

ash/common/system/tray/system_tray_notifier.h

Index: ash/common/system/tray/system_tray_notifier.h
diff --git a/ash/common/system/tray/system_tray_notifier.h b/ash/common/system/tray/system_tray_notifier.h
index 29bb9f521061c39977d5f613cee9636c32ef3d10..52ba695abd6d2556acdb3e15976a9b3656ac2f95 100644
--- a/ash/common/system/tray/system_tray_notifier.h
+++ b/ash/common/system/tray/system_tray_notifier.h
@@ -24,6 +24,7 @@ class AccessibilityObserver;
 class AudioObserver;
 class ClockObserver;
 class IMEObserver;
+class MaximizeModeScreenshotObserver;
 struct UpdateInfo;
 class UpdateObserver;
 class UserObserver;
@@ -97,6 +98,13 @@ class ASH_EXPORT SystemTrayNotifier {
   void NotifyUserUpdate();
   void NotifyUserAddedToSession();
 
+  // Maximize mode screenshot.
+  void AddMaximizeModeScreenshotObserver(
+      MaximizeModeScreenshotObserver* observer);
+  void RemoveMaximizeModeScreenshotObserver(
+      MaximizeModeScreenshotObserver* observer);
+  void NotifyWillTakeScreenshotInMaximizeMode();
+
 #if defined(OS_CHROMEOS)
   // Bluetooth.
   void AddBluetoothObserver(BluetoothObserver* observer);
@@ -174,6 +182,8 @@ class ASH_EXPORT SystemTrayNotifier {
   base::ObserverList<ClockObserver> clock_observers_;
   base::ObserverList<IMEObserver> ime_observers_;
   base::ObserverList<LocaleObserver> locale_observers_;
+  base::ObserverList<MaximizeModeScreenshotObserver>
+      maximize_mode_screenshot_observers_;
   base::ObserverList<UpdateObserver> update_observers_;
   base::ObserverList<UserObserver> user_observers_;