[Fixed Position] Allow straight lines

Pad width/height to give enough space to draw straight
lines; fix usage of background for boxes. WTD-880.

platform/features/layout/src/elements/ElementFactory.js

@@ -12,10 +12,10 @@ define(
                     border: "transparent"
                 },
                 "fixed.line": {
-                    x: 0,
-                    y: 0,
-                    x2: 5,
-                    y2: 3
+                    x: 5,
+                    y: 9,
+                    x2: 6,
+                    y2: 6
                 },
                 "fixed.text": {
                     fill: "transparent",

platform/features/layout/src/elements/LineProxy.js

@@ -32,11 +32,11 @@ define(
             };
 
             proxy.width = function () {
-                return Math.max(element.x, element.x2) - proxy.x();
+                return Math.max(Math.abs(element.x - element.x2), 1);
             };
 
             proxy.height = function () {
-                return Math.max(element.y, element.y2) - proxy.y();
+                return Math.max(Math.abs(element.y - element.y2), 1);
             };
 
             proxy.x1 = function () {