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..b3835dbcb46906c9317b8fee20719139d305d808 100644
--- a/ash/common/system/audio/tray_audio.cc
+++ b/ash/common/system/audio/tray_audio.cc
@@ -45,14 +45,19 @@ TrayAudio::TrayAudio(SystemTray* system_tray,
     : TrayImageItem(system_tray, IDR_AURA_UBER_TRAY_VOLUME_MUTE, UMA_AUDIO),
       audio_delegate_(std::move(audio_delegate)),
       volume_view_(NULL),
-      pop_up_volume_view_(false) {
-  WmShell::Get()->system_tray_notifier()->AddAudioObserver(this);
+      pop_up_volume_view_(false),
+      hide_popup_(false) {
+  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
@@ -110,7 +115,12 @@ void TrayAudio::OnOutputNodeVolumeChanged(uint64_t /* node_id */,
     return;
   }
   pop_up_volume_view_ = true;
-  PopupDetailedView(kTrayPopupAutoCloseDelayInSeconds, false);
+  // When the OutputNodeVolumeChanged is caused by a volume restore after
+  // maximize mode screenshot, it should not cause UI popup.
+  if (!hide_popup_)
+    PopupDetailedView(kTrayPopupAutoCloseDelayInSeconds, false);
+  else
+    hide_popup_ = false;

[Daniel Erat, 2016/07/28 04:45:00]

this approach (hiding the next popup) feels a bit race-prone. it seems like it'd
be cleaner if the audio handler instead notified observers about whether the
change was user-initiated (in which case the popup should be shown) or automated
(in which case it shouldn't).

[Qiang(Joe) Xu, 2016/07/28 20:25:02]

done by moving the logic to cras_audio_handler

 }
 
 void TrayAudio::OnOutputMuteChanged(bool /* mute_on */, bool system_adjust) {
@@ -138,6 +148,11 @@ void TrayAudio::OnActiveInputNodeChanged() {
   Update();
 }
 
+void TrayAudio::OnWillTakeScreenshotInMaximizeMode() {
+  HideDetailedView();
+  hide_popup_ = true;
+}
+
 void TrayAudio::ChangeInternalSpeakerChannelMode() {
   // Swap left/right channel only if it is in Yoga mode.
   system::TrayAudioDelegate::AudioChannelMode channel_mode =