Kchmviewer (http://sourceforge.net/projects/kchmviewer/) Tango Toolbar Icons.

Icons integrated into iconstorage.cpp from Tango Icons pack with follow command:
cat ./a_icon_22x22.png | xxd -c 25 -ps -i -u | sed 's/0X/x/g' | sed 's/, //g' | sed 's/,//g' | sed 's/$/"/' | sed 's/ //' | sed 's/^/t"/' | sed 's/ //'

Under other linux you can replace iconstorage.cpp with one from archive and recompile kchmviewer-3.1-2