feat(di): components can self-publish via publishAs

modules/angular2/src/core/annotations_impl/annotations.js

@@ -815,6 +815,41 @@ export class Component extends Directive {
    */
   injectables:List;
 
+  // TODO(naomib): needs documentation
+  /**
+   * Dependency injection tokens that this component publishes _itself_ to its
+   * children in its view via the application injector.
+   *
+   * ## Examples
+   *
+   * Imagine you have parent component that implements the [RpcService]
+   * interface. It can pose as [RpcService] to its children. Child components
+   * do not need to know about this fact. They only need to declare their
+   * dependency on [RpcService] without knowing exactly how it is provided.
+   *
+   * ```
+   * @Component({
+   *   selector: 'parent',
+   *   publishAs: [RpcService]
+   * })
+   * @View({
+   *   template: '<child></child>',
+   *   directives: [Child]
+   * })
+   * class Parent implements RpcService {
+   * }
+   *
+   * @Component({
+   *   selector: 'child'
+   * })
+   * class Child {
+   *   // Just asks for RpcService; doesn't know that it's Parent.
+   *   constructor(RpcService rpc);
+   * }
+   * ```
+   */
+  publishAs:List;
+
   @CONST()
   constructor({
       selector,
@@ -827,6 +862,7 @@ export class Component extends Directive {
       lifecycle,
       changeDetection = DEFAULT,
       compileChildren = true,
+      publishAs
     }:{
       selector:string,
       properties:Object,
@@ -837,7 +873,8 @@ export class Component extends Directive {
       injectables:List,
       lifecycle:List,
       changeDetection:string,
-      compileChildren:boolean
+      compileChildren:boolean,
+      publishAs:List
     }={})
   {
     super({
@@ -853,6 +890,7 @@ export class Component extends Directive {
 
     this.changeDetection = changeDetection;
     this.injectables = injectables;
+    this.publishAs = publishAs;
   }
 }