/usr/include/firefox/mozilla/net/ is in firefox-dev 11.0+build1-0ubuntu4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/firefox/mozilla/net/BaseWebSocketChannel.h
/usr/include/firefox/mozilla/net/ChannelEventQueue.h
/usr/include/firefox/mozilla/net/CookieServiceChild.h
/usr/include/firefox/mozilla/net/CookieServiceParent.h
/usr/include/firefox/mozilla/net/FTPChannelChild.h
/usr/include/firefox/mozilla/net/FTPChannelParent.h
/usr/include/firefox/mozilla/net/HttpBaseChannel.h
/usr/include/firefox/mozilla/net/HttpChannelChild.h
/usr/include/firefox/mozilla/net/HttpChannelParent.h
/usr/include/firefox/mozilla/net/NeckoChild.h
/usr/include/firefox/mozilla/net/NeckoCommon.h
/usr/include/firefox/mozilla/net/NeckoMessageUtils.h
/usr/include/firefox/mozilla/net/NeckoParent.h
/usr/include/firefox/mozilla/net/PHttpChannelParams.h
/usr/include/firefox/mozilla/net/WebSocketChannel.h
/usr/include/firefox/mozilla/net/WebSocketChannelChild.h
/usr/include/firefox/mozilla/net/WebSocketChannelParent.h
/usr/include/firefox/mozilla/net/WyciwygChannelChild.h
/usr/include/firefox/mozilla/net/WyciwygChannelParent.h