fix(router.ats): expose "navigating" property

src/router.ats

@@ -76,12 +76,22 @@ class Router {
       return Promise.reject();
     }
 
-    instruction.router = this;
+    this._startNavigating();
 
+    instruction.router = this;
     return this.pipeline.process(instruction)
+        .then(() => this._finishNavigating(), () => this._finishNavigating())
         .then(() => instruction.canonicalUrl);
   }
 
+  _startNavigating() {
+    this.navigating = true;
+  }
+
+  _finishNavigating() {
+    this.navigating = false;
+  }
+
 
   makeDescendantRouters(instruction) {
     this.traverseInstructionSync(instruction, (instruction, childInstruction) => {

test/router-viewport.es5.spec.js

@@ -600,6 +600,20 @@ describe('ngViewport', function () {
     expect(elt.text()).toBe('one');
   }));
 
+
+  it('should expose a "navigating" property on $router', function () {
+    $router.config([
+      { path: '/one', component: 'one' }
+    ]);
+    compile('<div ng-viewport></div>');
+
+    $router.navigate('/one');
+    expect($router.navigating).toBe(true);
+    $rootScope.$digest();
+    expect($router.navigating).toBe(false);
+  });
+
+
   function registerComponent(name, template, config) {
     if (!template) {
       template = '';