Fix native image recreated on layout even if the view is not resized

apps/tests/ui/view/view-tests.ios.ts

@@ -1,6 +1,12 @@
 import commonTests = require("./view-tests-common");
 import view = require("ui/core/view");
 
+import grid = require("ui/layouts/grid-layout");
+import color = require("color");
+import helper = require("../helper");
+import page = require("ui/page");
+import TKUnit = require("../../TKUnit");
+
 global.moduleMerge(commonTests, exports);
 
 export function getNativeBorderWidth(v: view.View): number {
@@ -27,4 +33,55 @@ export function checkNativeBackgroundColor(v: view.View): boolean {
 
 export function checkNativeBackgroundImage(v: view.View): boolean {
     return (<UIView>v.ios).backgroundColor !== undefined;
-}
+}
+
+export function testBackgroundInternalChangedOnceOnResize() {
+    
+    var layout = new grid.GridLayout();
+    layout.className = "myClass";
+    layout.backgroundColor = new color.Color(255, 255, 0, 0);
+    
+    var pageFactory = () => {
+        var root = new page.Page();
+        root.css = ".myClass { background-image: url('~/tests/logo.png') }";
+        root.content = layout;
+        return root;
+    }
+
+    helper.navigate(pageFactory);
+    
+    try {
+        var sizeChangedCount = 0;
+        function trackCount() {
+            var result = sizeChangedCount;
+            sizeChangedCount = 0;
+            return result;
+        }
+        
+        var base = (<any>layout.style)._applyStyleProperty;
+        (<any>layout.style)._applyStyleProperty = function(property) {
+            base.apply(layout.style, arguments);
+            if (property.name === "_backgroundInternal") {
+                ++sizeChangedCount;
+            }
+        }
+        
+        layout.requestLayout();
+        layout.layout(0, 0, 200, 200);
+        
+        TKUnit.assertEqual(trackCount(), 1, "Expected background to be re-applied at most once when the view is layed-out on 0 0 200 200.");
+        
+        layout.requestLayout();
+        layout.layout(50, 50, 250, 250);
+        
+        TKUnit.assertEqual(trackCount(), 0, "Expected background to NOT change when view is layed-out from 0 0 200 200 to 50 50 250 250.");
+        
+        layout.requestLayout();
+        layout.layout(0, 0, 250, 250);
+        
+        TKUnit.assertEqual(trackCount(), 1, "Expected background to be re-applied at most once when the view is layed-out from 50 50 250 250 to 0 0 250 250.");
+    }
+    finally {
+        helper.goBack();
+    }
+}