feat(ngInclude): $includeContentRequested event

Adding a $includeContentRequested event in order to better keep track of
how many includes are sent and be able to compare it with how many have
finished.

src/ng/directive/ngInclude.js

@@ -114,6 +114,16 @@
  */
 
 
+/**
+ * @ngdoc event
+ * @name ng.directive:ngInclude#$includeContentRequested
+ * @eventOf ng.directive:ngInclude
+ * @eventType emit on the scope ngInclude was declared in
+ * @description
+ * Emitted every time the ngInclude content is requested.
+ */
+
+
 /**
  * @ngdoc event
  * @name ng.directive:ngInclude#$includeContentLoaded
@@ -170,6 +180,7 @@ var ngIncludeDirective = ['$http', '$templateCache', '$anchorScroll', '$compile'
             }).error(function() {
               if (thisChangeId === changeCounter) clearContent();
             });
+            scope.$emit('$includeContentRequested');
           } else {
             clearContent();
           }

test/ng/directive/ngIncludeSpec.js

@@ -59,6 +59,22 @@ describe('ngInclude', function() {
     expect(element.text()).toEqual('');
   }));
 
+  it('should fire $includeContentRequested event on scope after making the xhr call', inject(
+      function ($rootScope, $compile, $httpBackend) {
+    var contentRequestedSpy = jasmine.createSpy('content requested').andCallFake(function (event) {
+        expect(event.targetScope).toBe($rootScope);
+    });
+
+    $httpBackend.whenGET('url').respond('my partial');
+    $rootScope.$on('$includeContentRequested', contentRequestedSpy);
+
+    element = $compile('<ng:include src="\'url\'"></ng:include>')($rootScope);
+    $rootScope.$digest();
+
+    expect(contentRequestedSpy).toHaveBeenCalledOnce();
+
+    $httpBackend.flush();
+  }));
 
   it('should fire $includeContentLoaded event on child scope after linking the content', inject(
       function($rootScope, $compile, $templateCache) {