Add an option to disable built-in AEC to AppRTC Android Demo

webrtc/examples/androidapp/res/values/strings.xml

 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <string name="app_name" translatable="false">AppRTC</string>
     <string name="settings_name" translatable="false">AppRTC Settings</string>
     <string name="disconnect_call">Disconnect Call</string>
     <string name="room_description">
         Please enter a room name. Room names are shared with everyone, so think
         of something unique and send it to a friend.
     </string>
     <string name="favorites">Favorites</string>
@@ skipping 99 matching lines @@
     <string name="pref_aecdump_key">aecdump_preference</string>
     <string name="pref_aecdump_title">Create aecdump.</string>
     <string name="pref_aecdump_dlg">Enable diagnostic audio recordings.</string>
     <string name="pref_aecdump_default">false</string>
 
     <string name="pref_opensles_key">opensles_preference</string>
     <string name="pref_opensles_title">Use OpenSL ES for audio playback.</string>
     <string name="pref_opensles_dlg">Use OpenSL ES for audio playback.</string>
     <string name="pref_opensles_default">false</string>
 
+    <string name="pref_disable_built_in_aec_key">disable_built_in_aec_preference</string>
+    <string name="pref_disable_built_in_aec_title">Disable built-in AEC.</string>
+    <string name="pref_disable_built_in_aec_dlg">Disable built-in AEC.</string>
+    <string name="pref_disable_built_in_aec_default">false</string>
+    <string name="pref_built_in_aec_not_available">Built-in AEC is not available</string>
+
     <string name="pref_miscsettings_key">misc_settings_key</string>
     <string name="pref_miscsettings_title">Miscellaneous settings.</string>
 
     <string name="pref_room_server_url_key">room_server_url_preference</string>
     <string name="pref_room_server_url_title">Room server URL.</string>
     <string name="pref_room_server_url_dlg">Enter a room server URL.</string>
     <string name="pref_room_server_url_default" translatable="false">https://appr.tc</string>
 
     <string name="pref_displayhud_key">displayhud_preference</string>
     <string name="pref_displayhud_title">Display call statistics.</string>
     <string name="pref_displayhud_dlg">Display call statistics.</string>
     <string name="pref_displayhud_default" translatable="false">false</string>
 
     <string name="pref_tracing_key">tracing_preference</string>
     <string name="pref_tracing_title">Debug performance tracing.</string>
     <string name="pref_tracing_dlg">Debug performance tracing.</string>
     <string name="pref_tracing_default" translatable="false">false</string>
 
 </resources>