Fix Volume slider is captured in screenshot done in touchview mode

ash/common/system/tray/system_tray.h

Index: ash/common/system/tray/system_tray.h
diff --git a/ash/common/system/tray/system_tray.h b/ash/common/system/tray/system_tray.h
index 9029cb16f70f1bdc8e728bd069cfb97fd7b382cf..a8bc7996c0e2848c0773cff4391e8e0b5e9cb3ec 100644
--- a/ash/common/system/tray/system_tray.h
+++ b/ash/common/system/tray/system_tray.h
@@ -25,6 +25,7 @@ class SystemBubbleWrapper;
 class SystemTrayDelegate;
 class SystemTrayItem;
 class TrayAccessibility;
+class TrayAudio;
 class TrayCast;
 class TrayDate;
 class TrayUpdate;
@@ -74,8 +75,9 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
   // seconds.
   void SetDetailedViewCloseDelay(int close_delay);
 
-  // Hides the detailed view for |item|.
-  void HideDetailedView(SystemTrayItem* item);
+  // Hides the detailed view for |item|. If |animate| is false, disable
+  // the hiding animation for hiding |item|.
+  void HideDetailedView(SystemTrayItem* item, bool animate);
 
   // Shows the notification view for |item|.
   void ShowNotificationView(SystemTrayItem* item);
@@ -121,6 +123,9 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
   // otherwise.
   views::View* GetHelpButtonView() const;
 
+  // Accessor for tray audio, can be null if !defined(OS_CHROMEOS).

[Daniel Erat, 2016/08/01 21:10:06]

nit: i wouldn't mention the ifdef here, since it might become out of date. how
about something like this instead?

  // Returns TrayAudio object if present or null otherwise.

[Qiang(Joe) Xu, 2016/08/01 22:56:47]

Done.

+  TrayAudio* GetTrayAudio() const;
+
   // Accessors for testing.
 
   // Returns true if the bubble exists.
@@ -248,6 +253,7 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
   bool full_system_tray_menu_;
 
   TrayAccessibility* tray_accessibility_;  // not owned

[Daniel Erat, 2016/08/01 21:10:06]

nit: if none of these are owned, do you mind moving the "not owned" comment to
the previous line so it's at the top of the block?

  // These objects are not owned by this class.
  TrayAccessibility* ...;
  TrayAudio* ...;
  ...

[Qiang(Joe) Xu, 2016/08/01 22:56:47]

Done.

+  TrayAudio* tray_audio_;

[Daniel Erat, 2016/08/01 21:10:06]

nit: document that this may be null, e.g.

  TrayAudio* tray_audio_;  // May be null.

[Qiang(Joe) Xu, 2016/08/01 22:56:47]

Done.

   TrayCast* tray_cast_;
   TrayDate* tray_date_;
   TrayUpdate* tray_update_;