Refactor the TrayAudio code so that it can be used by other platforms.

chrome/browser/ui/ash/system_tray_delegate_chromeos.cc

Index: chrome/browser/ui/ash/system_tray_delegate_chromeos.cc
diff --git a/chrome/browser/ui/ash/system_tray_delegate_chromeos.cc b/chrome/browser/ui/ash/system_tray_delegate_chromeos.cc
index 202ca5b41ad063146e27fd46bfa3535c585138c1..c50ebdbf67d229dd6398d751b25396d696d35a04 100644
--- a/chrome/browser/ui/ash/system_tray_delegate_chromeos.cc
+++ b/chrome/browser/ui/ash/system_tray_delegate_chromeos.cc
@@ -89,6 +89,7 @@
 #include "chrome/browser/upgrade_detector.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
+#include "chromeos/audio/cras_audio_handler.h"
 #include "chromeos/chromeos_switches.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/session_manager_client.h"
@@ -292,6 +293,8 @@ SystemTrayDelegateChromeOS::SystemTrayDelegateChromeOS()
       this,
       chrome::NOTIFICATION_CROS_ACCESSIBILITY_TOGGLE_VIRTUAL_KEYBOARD,
       content::NotificationService::AllSources());
+
+  CrasAudioHandler::Get()->AddAudioObserver(this);
 }
 
 void SystemTrayDelegateChromeOS::Initialize() {
@@ -369,6 +372,8 @@ SystemTrayDelegateChromeOS::~SystemTrayDelegateChromeOS() {
   // Stop observing Drive operations.
   UnobserveDriveUpdates();
 
+  CrasAudioHandler::Get()->RemoveAudioObserver(this);
+
   policy::BrowserPolicyConnectorChromeOS* connector =
       g_browser_process->platform_part()->browser_policy_connector_chromeos();
   policy::DeviceCloudPolicyManagerChromeOS* policy_manager =
@@ -1202,6 +1207,33 @@ void SystemTrayDelegateChromeOS::InputMethodPropertyChanged(
   GetSystemTrayNotifier()->NotifyRefreshIME(false);
 }
 
+// Overridden from CrasAudioHandler::AudioObserver.
+void SystemTrayDelegateChromeOS::OnOutputVolumeChanged() {
+  GetSystemTrayNotifier()->NotifyAudioOutputVolumeChanged();
+}
+
+void SystemTrayDelegateChromeOS::OnOutputMuteChanged() {
+  GetSystemTrayNotifier()->NotifyAudioOutputMuteChanged();
+}
+
+void SystemTrayDelegateChromeOS::OnInputGainChanged() {
+}
+
+void SystemTrayDelegateChromeOS::OnInputMuteChanged() {
+}
+
+void SystemTrayDelegateChromeOS::OnAudioNodesChanged() {
+  GetSystemTrayNotifier()->NotifyAudioNodesChanged();
+}
+
+void SystemTrayDelegateChromeOS::OnActiveOutputNodeChanged() {
+  GetSystemTrayNotifier()->NotifyAudioActiveOutputNodeChanged();
+}
+
+void SystemTrayDelegateChromeOS::OnActiveInputNodeChanged() {
+  GetSystemTrayNotifier()->NotifyAudioActiveInputNodeChanged();
+}
+
 // drive::JobListObserver overrides.
 void SystemTrayDelegateChromeOS::OnJobAdded(const drive::JobInfo& job_info) {
   OnJobUpdated(job_info);