fix($rootScope): broadcast $destroy event on $rootScope

Fixes angular#5169

Author: jeffbcross

src/ng/rootScope.js

@@ -670,11 +670,12 @@ function $RootScopeProvider(){
        */
       $destroy: function() {
         // we can't destroy the root scope or a scope that has been already destroyed
-        if ($rootScope == this || this.$$destroyed) return;
+        if (this.$$destroyed) return;
         var parent = this.$parent;
 
         this.$broadcast('$destroy');
         this.$$destroyed = true;
+        if (this === $rootScope) return;
 
         if (parent.$$childHead == this) parent.$$childHead = this.$$nextSibling;
         if (parent.$$childTail == this) parent.$$childTail = this.$$prevSibling;

test/ng/rootScopeSpec.js

@@ -599,10 +599,14 @@ describe('Scope', function() {
     }));
 
 
-    it('should ignore remove on root', inject(function($rootScope) {
+    it('should broadcast $destroy on rootScope', inject(function($rootScope) {
+      var spy = spyOn(angular, 'noop');
+      $rootScope.$on('$destroy', angular.noop);
       $rootScope.$destroy();
       $rootScope.$digest();
       expect(log).toEqual('123');
+      expect(spy).toHaveBeenCalled();
+      expect($rootScope.$$destroyed).toBe(true);
     }));