[Fixed Position] Add ability to work in pixel space

Fix code style issues per Victor's review

Add toggle to work in pixel space or grid space, per the issue description.
Each element stores a boolean property that determines whether or not it
snaps to grid space or pixel space. Coordinates are converted between spaces
on toggle, preserving the size of the element in pixels.

To complete: change UI element for toggle to a checkbox.

platform/features/layout/src/FixedController.js

@@ -75,7 +75,7 @@ define(
             // Convert from element x/y/width/height to an
             // appropriate ng-style argument, to position elements.
             function convertPosition(elementProxy) {
-                var gridSize = self.gridSize;
+                var gridSize = elementProxy.getGridSize();
                 // Multiply position/dimensions by grid size
                 return {
                     left: (gridSize[0] * elementProxy.x()) + 'px',
@@ -114,6 +114,7 @@ define(
                 self.gridSize = layoutGrid;
 
                 self.elementProxies.forEach(function (elementProxy) {
+                    elementProxy.setGridSize(self.gridSize);
                     elementProxy.style = convertPosition(elementProxy);
                 });
             }
@@ -121,7 +122,7 @@ define(
             // Decorate an element for display
             function makeProxyElement(element, index, elements) {
                 var ElementProxy = ElementProxies[element.type],
-                    e = ElementProxy && new ElementProxy(element, index, elements);
+                    e = ElementProxy && new ElementProxy(element, index, elements, self.gridSize);
 
                 if (e) {
                     // Provide a displayable position (convert from grid to px)
@@ -254,7 +255,8 @@ define(
                     color: "",
                     titled: true,
                     width: DEFAULT_DIMENSIONS[0],
-                    height: DEFAULT_DIMENSIONS[1]
+                    height: DEFAULT_DIMENSIONS[1],
+                    useGrid: true
                 });
 
                 //Re-initialize objects, and subscribe to new object
@@ -518,4 +520,3 @@ define(
         return FixedController;
     }
 );
-