This happens when I run 'emerge compiz':

The following USE changes are necessary to proceed:
(see "package.use" in the portage(5) man page for more details)

1. required by x11-wm/metacity-2.34.13
2. required by x11-wm/compiz-0.9.11[-gnome,-gtk]
3. required by compiz (argument)
   >=media-libs/libcanberra-0.30-r1 gtk

!!! The ebuild selected to satisfy ">=net-libs/webkit-gtk-1.4.0:3" has unmet requirements.

• net-libs/webkit-gtk-2.4.4::gentoo USE="X egl geoloc gstreamer jit opengl webgl (-aqua) -coverage -debug -gles2 -introspection -libsecret -spell -test -wayland"

The following REQUIRED_USE flag constraints are unsatisfied:
geoloc? ( introspection )

The above constraints are a subset of the following complete expression:
geoloc? ( introspection ) introspection? ( gstreamer ) gles2? ( egl ) webgl? ( exactly-one-of ( gles2 opengl ) ) !webgl? ( at-most-one-of ( gles2 opengl ) ) any-of ( aqua wayland X )

(dependency required by "gnome-extra/zenity-3.8.0-r2[webkit]" [ebuild])
(dependency required by "x11-wm/metacity-2.34.13" [ebuild])
(dependency required by "x11-wm/compiz-0.9.11[-gnome,-gtk]" [ebuild])
(dependency required by "compiz" [argument])