fix min width of filetree scrollbar

plugins/c9.ide.tree/style.css

@@ -20,7 +20,7 @@
     color : @selected-color;
 }
 
-.filetree .tree-row.projectRoot, .filetree .tree-row:first-child {
+.filetree .tree-row.projectRoot:first-child {
     margin-right: @tree-first-row-margin-right;
 }
 

plugins/c9.ide.tree/tree.js

@@ -277,6 +277,7 @@ define(function(require, exports, module) {
             btnTreeSettings.setAttribute("submenu", mnuFilesSettings);
             tree.renderer.on("scrollbarVisibilityChanged", updateScrollBarSize);
             tree.renderer.on("resize", updateScrollBarSize);
+            tree.renderer.scrollBarV.$minWidth = 10;
             function updateScrollBarSize() {
                 var scrollBarV = tree.renderer.scrollBarV;
                 var w = scrollBarV.isVisible ? scrollBarV.getWidth() : 0;