fix($location): strip off empty hash segments when comparing

Backported from e93710fe0e

The url is the same whether or not there is an empty `#` marker at the end.
This prevents unwanted calls to update the browser, since the browser is
automatically applying an empty hash if necessary to prevent page reloads.

Closes #9635
Closes #10748

src/ng/location.js

@@ -68,6 +68,10 @@ function stripHash(url) {
   return index == -1 ? url : url.substr(0, index);
 }
 
+function trimEmptyHash(url) {
+  return url.replace(/(#.+)|#$/, '$1');
+}
+
 
 function stripFile(url) {
   return url.substr(0, stripHash(url).lastIndexOf('/') + 1);
@@ -724,10 +728,11 @@ function $LocationProvider(){
     // update browser
     var changeCounter = 0;
     $rootScope.$watch(function $locationWatch() {
-      var oldUrl = $browser.url();
+      var oldUrl = trimEmptyHash($browser.url());
+      var newUrl = trimEmptyHash($location.absUrl());
       var currentReplace = $location.$$replace;
 
-      if (!changeCounter || oldUrl != $location.absUrl()) {
+      if (!changeCounter || oldUrl != newUrl) {
         changeCounter++;
         $rootScope.$evalAsync(function() {
           if ($rootScope.$broadcast('$locationChangeStart', $location.absUrl(), oldUrl).

test/ng/locationSpec.js

@@ -550,6 +550,20 @@ describe('$location', function() {
     };
   }
 
+  describe('location watch', function() {
+    beforeEach(initService({supportHistory: true}));
+    beforeEach(inject(initBrowser({url:'http://new.com/a/b#'})));
+
+    it('should not update browser if only the empty hash fragment is cleared by updating the search', inject(function($rootScope, $browser, $location) {
+      $rootScope.$digest();
+
+      $browser.url('http://new.com/a/b#');
+      var $browserUrl = spyOnlyCallsWithArgs($browser, 'url').andCallThrough();
+      $rootScope.$digest();
+      expect($browserUrl).not.toHaveBeenCalled();
+    }));
+  });
+
   describe('wiring', function() {
 
     beforeEach(initService({html5Mode:false,hashPrefix: '!',supportHistory: true}));