/usr/include/firefox/mozilla/gfx/ is in firefox-dev 11.0+build1-0ubuntu4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/firefox/mozilla/gfx/2D.h
/usr/include/firefox/mozilla/gfx/BaseMargin.h
/usr/include/firefox/mozilla/gfx/BasePoint.h
/usr/include/firefox/mozilla/gfx/BasePoint3D.h
/usr/include/firefox/mozilla/gfx/BasePoint4D.h
/usr/include/firefox/mozilla/gfx/BaseRect.h
/usr/include/firefox/mozilla/gfx/BaseSize.h
/usr/include/firefox/mozilla/gfx/Blur.h
/usr/include/firefox/mozilla/gfx/Matrix.h
/usr/include/firefox/mozilla/gfx/PathHelpers.h
/usr/include/firefox/mozilla/gfx/Point.h
/usr/include/firefox/mozilla/gfx/Rect.h
/usr/include/firefox/mozilla/gfx/SharedDIB.h
/usr/include/firefox/mozilla/gfx/Types.h