OS X Ｃhanging eclipse(Mars) project explorer tree view font size
Open Finder
right mouse click eclipse.app , click 顯示套件內容
open file Eclipse.app/Contents/Eclipse/plugins/org.eclipse.ui.themes_1.1.1.v20151026-1355/css/e4_basestyle.css
There I added :
.MPart Tree {
font-size: 13;
}