Review SCSS refactoring for to-be-deprecated Bourbon functions (#1959)

* [Frontend] Refactor SCSS to remove deprecated @includes

Fixes #1891
- In progress

* [Frontend] Refactor SCSS to remove deprecated @includes

Fixes #1891
Making bourbon happy by refactoring to-be-deprecated
calls to prefixing @includes:
- transform and related CSS;
- flex and related CSS;
- Fixed double semi-colons to single;

platform/commonUI/general/res/sass/mobile/_tree.scss

@@ -34,7 +34,18 @@ body.touch {
 		line-height: $mobileTreeItemH !important;
 		.view-control {
             font-size: 1em;
-            width: ceil($mobileTreeItemH * 0.5);
+            margin-right: $interiorMargin;
+            width: ceil($mobileTreeItemH * 0.75);
+            &.has-children {
+                &:before {
+                    content: $glyph-icon-arrow-down;
+                    left: 50%;
+                    transform: translateX(-50%) rotate(-90deg);
+                }
+                &.expanded:before {
+                    transform: translateX(-50%) rotate(0deg);
+                }
+            }
 		}
 		.t-object-label {
 			line-height: inherit;