DevTools: defer styles delta calculation to until the end of the task.

LayoutTests/inspector/elements/styles/styles-test.js

 function initialize_StylesTests()
 {
 
 InspectorTest.waitForStylesheetsOnFrontend = function(styleSheetsCount, callback)
 {
-    function styleSheetComparator(a, b)
-    {
-        if (a.sourceURL < b.sourceURL)
-            return -1;
-        else if (a.sourceURL > b.sourceURL)
-            return 1;
-        return a.startLine - b.startLine || a.startColumn - b.startColumn;
-    }
-
     var styleSheets = WebInspector.cssModel.allStyleSheets();
     if (styleSheets.length >= styleSheetsCount) {
-        styleSheets.sort(styleSheetComparator);
         callback(styleSheets);
         return;
     }
 
     function onStyleSheetAdded()
     {
         var styleSheets = WebInspector.cssModel.allStyleSheets();
         if (styleSheets.length < styleSheetsCount)
             return;
 
         WebInspector.cssModel.removeEventListener(WebInspector.CSSStyleModel.Events.StyleSheetAdded, onStyleSheetAdded, this);
         styleSheets.sort(styleSheetComparator);
         callback(null, styleSheets);
     }
 
     WebInspector.cssModel.addEventListener(WebInspector.CSSStyleModel.Events.StyleSheetAdded, onStyleSheetAdded, this);
 }
 
 }