fix($compile): retain CSS classes added in clone fn on async directive

In synchronous directives (without a templateUrl), classes added to the node
during the clone attach function persist in the post-link function.

Before this patch, classes addedd to asynchronous templates during the clone
attach function would not persist after the node is replaced with the template
prior to linking.

Fixes angular#5439

Author: caitp

src/ng/compile.js

@@ -1707,9 +1707,13 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
                 linkNode = $compileNode[0];
 
             if (beforeTemplateLinkNode !== beforeTemplateCompileNode) {
+              var oldClasses = beforeTemplateLinkNode.className;
               // it was cloned therefore we have to clone as well.
               linkNode = jqLiteClone(compileNode);
               replaceWith(linkRootElement, jqLite(beforeTemplateLinkNode), linkNode);
+
+              // Copy in CSS classes from original node
+              safeAddClass(jqLite(linkNode), oldClasses);
             }
             if (afterTemplateNodeLinkFn.transclude) {
               childBoundTranscludeFn = createBoundTranscludeFn(scope, afterTemplateNodeLinkFn.transclude);

test/ng/compileSpec.js

@@ -1128,6 +1128,35 @@ describe('$compile', function() {
         });
 
 
+        it('should copy classes from pre-template node into linked element', function() {
+          module(function() {
+            directive('outer', function($compile, $parse) {
+              return function(scope, element, attr) {
+                var template = $compile('<div inner></div>');
+                template(scope, function(node) {
+                  element.append(node);
+                  node.addClass('from-outer');
+                });
+              };
+            });
+
+            directive('inner', valueFn({
+              templateUrl: 'inner.html',
+              replace: true
+            }));
+          });
+          inject(function($compile, $templateCache, $rootScope) {
+            var child;
+            $templateCache.put('inner.html', '<p class="inner">Hello</p>');
+            element = $compile('<div outer></div>')($rootScope);
+            $rootScope.$digest();
+            child = element.children('p').eq(0);
+            expect(child).toHaveClass('from-outer');
+            expect(child).toHaveClass('inner');
+          });
+        });
+
+
         describe('delay compile / linking functions until after template is resolved', function(){
           var template;
           beforeEach(module(function() {