Fix bug in shifted box.

Runtime/rendering/shifted_box.cs

         public float? widthFactor {
             get { return this._widthFactor; }
             set {
-                if (this._widthFactor != value) {
+                if (this._widthFactor == value) {
                     return;
                 }
 
         public float? heightFactor {
             get { return this._heightFactor; }
             set {
-                if (this._heightFactor != value) {
+                if (this._heightFactor == value) {
                     return;
                 }
 
         public float baseline {
             get { return this._baseline; }
             set {
-                if (this._baseline != value) {
+                if (this._baseline == value) {
                     return;
                 }
 
         public TextBaseline baselineType {
             get { return this._baselineType; }
             set {
-                if (this._baselineType != value) {
+                if (this._baselineType == value) {
                     return;
                 }