gtk: Revert menu icon changes.

This reverts commit 8c79983155ac820227acaaf8cd006df41e4f2b12.

I didn't realize it, but we still need icons in at least one
GTK menu: the network one.  I'll have to find another way to
clean up the menus.

BUG=chromium-os:4345
TEST=none
TBR=xiyuan

Review URL: http://codereview.chromium.org/4778001

Change-Id: I0f675d648f7e436d7588fe999935ae049256399a
1 file changed