feat(uiView): cache and test autoscroll expression

Changes to follow ngInclude's behavior more closely (like #714):

- memorizes the autoscroll expression, since it's not supposed to be
  changed once the template is compiled, only the evaluated
  expression should change;
- the page won't autoscroll when the attribute isn't present, which
  is a breaking change from the current implementation.

src/viewDirective.js

@@ -31,6 +31,7 @@ function $ViewDirective(   $state,   $compile,   $controller,   $injector,   $an
         var viewScope, viewLocals,
             name = attr[directive.name] || attr.name || '',
             onloadExp = attr.onload || '',
+            autoscrollExp = attr.autoscroll,
             animate = $animator && $animator(scope, attr),
             initialView = transclude(scope);
 
@@ -123,7 +124,7 @@ function $ViewDirective(   $state,   $compile,   $controller,   $injector,   $an
 
           // TODO: This seems strange, shouldn't $anchorScroll listen for $viewContentLoaded if necessary?
           // $anchorScroll might listen on event...
-          if (!angular.isDefined(attr.autoscroll) || (!attr.autoscroll || scope.$eval(attr.autoscroll))) {
+          if (angular.isDefined(autoscrollExp) && (!autoscrollExp || scope.$eval(autoscrollExp))) {
             $anchorScroll();
           }
         }

test/viewDirectiveSpec.js

@@ -216,11 +216,11 @@ describe('uiView', function () {
   });
 
   describe('autoscroll attribute', function () {
-    it('should autoscroll when unspecified', inject(function ($state, $q, $anchorScroll) {
+    it('should not autoscroll when unspecified', inject(function ($state, $q, $anchorScroll) {
       elem.append($compile('<div ui-view></div>')(scope));
       $state.transitionTo(gState);
       $q.flush();
-      expect($anchorScroll).toHaveBeenCalled();
+      expect($anchorScroll).not.toHaveBeenCalled();
     }));
 
     it('should autoscroll when expr is missing', inject(function ($state, $q, $anchorScroll) {
@@ -230,15 +230,17 @@ describe('uiView', function () {
       expect($anchorScroll).toHaveBeenCalled();
     }));
 
-    it('should autoscroll when truthy', inject(function ($state, $q, $anchorScroll) {
-      elem.append($compile('<div ui-view autoscroll="true"></div>')(scope));
+    it('should autoscroll when expression is truthy', inject(function ($state, $q, $anchorScroll) {
+      elem.append($compile('<div ui-view autoscroll="doAutoScroll"></div>')(scope));
+      scope.doAutoScroll = true;
       $state.transitionTo(gState);
       $q.flush();
       expect($anchorScroll).toHaveBeenCalled();
     }));
 
-    it('should not autoscroll when falsy', inject(function ($state, $q, $anchorScroll) {
-      elem.append($compile('<div ui-view autoscroll="false"></div>')(scope));
+    it('should not autoscroll when expression is falsy', inject(function ($state, $q, $anchorScroll) {
+      elem.append($compile('<div ui-view autoscroll="doAutoScroll()"></div>')(scope));
+      scope.doAutoScroll = function () { return false; };
       $state.transitionTo(gState);
       $q.flush();
       expect($anchorScroll).not.toHaveBeenCalled();