/indra/newview/skins/default/xui/en/panel_adhoc_control_panel.xml

<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
<panel
 border="false"
 follows="all"
 height="215"
 name="panel_im_control_panel"
 width="150">
    <layout_stack
     mouse_opaque="false"
     border_size="0"
     clip="false"
     follows="all"
     height="215"
     layout="topleft"
     left="3"
     name="vertical_stack"
     orientation="vertical"
     top="0"
     width="147">
        <layout_panel
         auto_resize="true"
         follows="top|left"
         height="130"
         layout="topleft"
         left="0"
         min_height="0"
         mouse_opaque="false"
         width="147"
         top="0"
         name="speakers_list_panel">
            <avatar_list
             color="DkGray2"
             follows="all"
             height="130"
             ignore_online_status="true"
             layout="topleft"
             name="speakers_list"
             opaque="false"
             show_info_btn="true"
             show_profile_btn="false"
             show_speaking_indicator="false"
             width="147" />
        </layout_panel>
        <layout_panel
         auto_resize="false"
         follows="top|left|right"
         height="25"
         layout="topleft"
         min_height="25"
         width="130"
         name="call_btn_panel"
         visible="false">
            <button
             follows="all"
             height="20"
             label="Call"
             name="call_btn"
             width="130"
             top="0" />
        </layout_panel>
        <layout_panel
         auto_resize="false"
         follows="top|left|right"
         height="25"
         layout="topleft"
         min_height="25"
         width="130"
         name="end_call_btn_panel"
         visible="false">
            <button
             follows="all"
             height="20"
             label="Leave Call"
             name="end_call_btn"
             top="0"/>
        </layout_panel>
        <layout_panel
         auto_resize="false"
         follows="top|left|right"
         height="25"
         layout="topleft"
         min_height="25"
         width="130"
         name="voice_ctrls_btn_panel"
         visible="false">
            <button
             follows="all"
             height="20"
             label="Voice Controls"
             name="voice_ctrls_btn"
             top="0"
             use_ellipses="true" />
        </layout_panel>
    </layout_stack>
</panel>