• file

/home/gim/programs/eclipse/plugins/org.eclipse.platform_4.3.1.v20130911-1000/css/e4_default_gtk.css

• add

#org-eclipse-jdt-ui-PackageExplorer Tree,
#org-eclipse-ui-navigator-ProjectExplorer Tree,
#org-eclipse-ui-views-ContentOutline Tree {
  font-size: 9;
}

• edit

.MPartStack {
	font-size: 9;
	swt-simple: false;
	swt-mru-visible: false;
}