chore(core): introduce $$body service

This patch makes it easier to gain access to document.body
via the injector.

angularFiles.js

@@ -88,6 +88,7 @@ var angularFiles = {
   'angularModules': {
     'ngAnimate': [
       'src/ngAnimate/shared.js',
+      'src/ngAnimate/body.js',
       'src/ngAnimate/rafScheduler.js',
       'src/ngAnimate/animateChildrenDirective.js',
       'src/ngAnimate/animateCss.js',

src/ngAnimate/body.js

@@ -0,0 +1,7 @@
+'use strict';
+
+function $$BodyProvider() {
+  this.$get = ['$document', function($document) {
+    return jqLite($document[0].body);
+  }];
+}

src/ngAnimate/module.js

@@ -2,6 +2,7 @@
 
 /* global angularAnimateModule: true,
 
+   $$BodyProvider,
    $$rAFMutexFactory,
    $$rAFSchedulerFactory,
    $$AnimateChildrenDirective,
@@ -741,6 +742,8 @@
  * Click here {@link ng.$animate $animate to learn more about animations with `$animate`}.
  */
 angular.module('ngAnimate', [])
+  .provider('$$body', $$BodyProvider)
+
   .directive('ngAnimateChildren', $$AnimateChildrenDirective)
 
   .factory('$$rAFMutex', $$rAFMutexFactory)

test/ngAnimate/bodySpec.js

@@ -0,0 +1,9 @@
+'use strict';
+
+describe('$$body', function() {
+  beforeEach(module('ngAnimate'));
+
+  it("should inject $document", inject(function($$body, $document) {
+    expect($$body).toEqual(jqLite($document[0].body));
+  }));
+});