fix($anchorScroll): don't scroll to top when initializing and location hash is empty

Closes angular#8848
Closes angular#9393

Author: IgorMinar

src/ng/anchorScroll.js

@@ -94,7 +94,10 @@ function $AnchorScrollProvider() {
     // (no url change, no $location.hash() change), browser native does scroll
     if (autoScrollingEnabled) {
       $rootScope.$watch(function autoScrollWatch() {return $location.hash();},
-        function autoScrollWatchAction() {
+        function autoScrollWatchAction(newVal, oldVal) {
+          // skip the initial scroll if $location.hash is empty
+          if (newVal === oldVal && newVal === '') return;
+
           $rootScope.$evalAsync(scroll);
         });
     }

test/ng/anchorScrollSpec.js

@@ -106,6 +106,12 @@ describe('$anchorScroll', function() {
 
   describe('watcher', function() {
 
+    function initAnchorScroll() {
+      return function($rootScope, $anchorScroll) {
+        $rootScope.$digest();
+      };
+    }
+
     function initLocation(config) {
       return function($provide, $locationProvider) {
         $provide.value('$sniffer', {history: config.historyApi});
@@ -135,6 +141,7 @@ describe('$anchorScroll', function() {
     it('should scroll to element when hash change in hashbang mode', function() {
       module(initLocation({html5Mode: false, historyApi: true}));
       inject(
+        initAnchorScroll(),
         addElements('id=some'),
         changeHashTo('some'),
         expectScrollingTo('id=some')
@@ -145,16 +152,25 @@ describe('$anchorScroll', function() {
     it('should scroll to element when hash change in html5 mode with no history api', function() {
       module(initLocation({html5Mode: true, historyApi: false}));
       inject(
+        initAnchorScroll(),
         addElements('id=some'),
         changeHashTo('some'),
         expectScrollingTo('id=some')
       );
     });
 
 
+    it('should not scroll to the top if $anchorScroll is initializing and location hash is empty',
+      inject(
+        initAnchorScroll(),
+        expectNoScrolling())
+    );
+
+
     it('should not scroll when element does not exist', function() {
       module(initLocation({html5Mode: false, historyApi: false}));
       inject(
+        initAnchorScroll(),
         addElements('id=some'),
         changeHashTo('other'),
         expectNoScrolling()
@@ -165,6 +181,7 @@ describe('$anchorScroll', function() {
     it('should scroll when html5 mode with history api', function() {
       module(initLocation({html5Mode: true, historyApi: true}));
       inject(
+        initAnchorScroll(),
         addElements('id=some'),
         changeHashTo('some'),
         expectScrollingTo('id=some')