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..95769eef91035fe3a715554fca8f7a599f67c137 100644
--- a/ash/common/system/audio/tray_audio.cc
+++ b/ash/common/system/audio/tray_audio.cc
@@ -46,13 +46,17 @@ 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 +142,10 @@ void TrayAudio::OnActiveInputNodeChanged() {
   Update();
 }
 
+void TrayAudio::OnTakingScreenshotInMaximizeMode() {
+  HideDetailedView(false);
+}
+
 void TrayAudio::ChangeInternalSpeakerChannelMode() {
   // Swap left/right channel only if it is in Yoga mode.
   system::TrayAudioDelegate::AudioChannelMode channel_mode =