Fix Volume slider is captured in screenshot done in touchview mode

ash/common/system/audio/tray_audio.cc

Index: ash/common/system/audio/tray_audio.cc
diff --git a/ash/common/system/audio/tray_audio.cc b/ash/common/system/audio/tray_audio.cc
index 8ff0987aadc01be209d8ef02a09d83a1fd738b8a..af2a9d58ec7e9e1246691b2db6217e76ca2c62af 100644
--- a/ash/common/system/audio/tray_audio.cc
+++ b/ash/common/system/audio/tray_audio.cc
@@ -38,6 +38,8 @@
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/view.h"
 
+#include "ui/views/widget/widget.h"
+
 namespace ash {
 
 TrayAudio::TrayAudio(SystemTray* system_tray,
@@ -46,13 +48,17 @@ TrayAudio::TrayAudio(SystemTray* system_tray,
       audio_delegate_(std::move(audio_delegate)),
       volume_view_(NULL),
       pop_up_volume_view_(false) {
-  WmShell::Get()->system_tray_notifier()->AddAudioObserver(this);
+  SystemTrayNotifier* notifier = WmShell::Get()->system_tray_notifier();
+  notifier->AddAudioObserver(this);
+  notifier->AddMaximizeModeScreenshotObserver(this);
   display::Screen::GetScreen()->AddObserver(this);
 }
 
 TrayAudio::~TrayAudio() {
   display::Screen::GetScreen()->RemoveObserver(this);
-  WmShell::Get()->system_tray_notifier()->RemoveAudioObserver(this);
+  SystemTrayNotifier* notifier = WmShell::Get()->system_tray_notifier();
+  notifier->RemoveMaximizeModeScreenshotObserver(this);
+  notifier->RemoveAudioObserver(this);
 }
 
 // static
@@ -138,6 +144,10 @@ void TrayAudio::OnActiveInputNodeChanged() {
   Update();
 }
 
+void TrayAudio::OnWillTakeScreenshotInMaximizeMode() {
+  HideDetailedView(false);
+}
+
 void TrayAudio::ChangeInternalSpeakerChannelMode() {
   // Swap left/right channel only if it is in Yoga mode.
   system::TrayAudioDelegate::AudioChannelMode channel_mode =