Implemented system tray UI for new account management.

ash/system/tray/system_tray_delegate.h

Index: ash/system/tray/system_tray_delegate.h
diff --git a/ash/system/tray/system_tray_delegate.h b/ash/system/tray/system_tray_delegate.h
index fe0863bc4e100421cc96cc0950a4b15791ee8775..c492f1fbe3352320c2ee4eb4c00f155ee0118088 100644
--- a/ash/system/tray/system_tray_delegate.h
+++ b/ash/system/tray/system_tray_delegate.h
@@ -111,6 +111,10 @@ typedef std::vector<IMEInfo> IMEInfoList;
 
 class VolumeControlDelegate;
 
+namespace tray {
+class UserAccountsDelegate;
+}  // namespace tray
+
 class ASH_EXPORT SystemTrayDelegate {
  public:
   virtual ~SystemTrayDelegate() {}
@@ -333,7 +337,12 @@ class ASH_EXPORT SystemTrayDelegate {
 
   // Returns true when the Search key is configured to be treated as Caps Lock.
   virtual bool IsSearchKeyMappedToCapsLock() = 0;
+
+  // Returns accounts delegate for given user.
+  virtual tray::UserAccountsDelegate* GetUserAccountsDelegate(
+      const std::string& user_id) = 0;
 };
+
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_