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..3c356eb783f9f1b6c756c273fce19021402a9d86 100644
--- a/ash/common/system/audio/tray_audio.cc
+++ b/ash/common/system/audio/tray_audio.cc
@@ -38,6 +38,10 @@
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/view.h"
 
+#if defined(OS_CHROMEOS)
+#include "chromeos/audio/cras_audio_handler.h"
+#endif
+
 namespace ash {
 
 TrayAudio::TrayAudio(SystemTray* system_tray,
@@ -45,14 +49,20 @@ 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),
+      saved_volume_percent_(0) {
+  SystemTrayNotifier* notifier = WmShell::Get()->system_tray_notifier();
+  notifier->AddAudioObserver(this);
+  notifier->AddMaxModeScreenshotObserver(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->RemoveMaxModeScreenshotObserver(this);
+  notifier->RemoveAudioObserver(this);
 }
 
 // static
@@ -110,7 +120,12 @@ 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;
 }
 
 void TrayAudio::OnOutputMuteChanged(bool /* mute_on */, bool system_adjust) {
@@ -138,6 +153,22 @@ void TrayAudio::OnActiveInputNodeChanged() {
   Update();
 }
 
+void TrayAudio::OnWillTakeScreenshot(int volume_percent) {
+  saved_volume_percent_ = volume_percent;
+  HideDetailedView();
+}
+
+void TrayAudio::OnDidTakeScreenshot() {
+  hide_popup_ = true;
+#if defined(OS_CHROMEOS)
+  // Restore the volume to the value before volume-down modifier key is pressed
+  // to wait for power button.
+  chromeos::CrasAudioHandler* audio_handler = chromeos::CrasAudioHandler::Get();
+  DCHECK(audio_handler->IsInitialized());
+  audio_handler->SetOutputVolumePercent(saved_volume_percent_);
+#endif
+}
+
 void TrayAudio::ChangeInternalSpeakerChannelMode() {
   // Swap left/right channel only if it is in Yoga mode.
   system::TrayAudioDelegate::AudioChannelMode channel_mode =