Mojo JS Bindings: Update User's Guide, examples

examples/js/share_echo_target.js

+#!mojo:js_content_handler
+// Demonstrate sharing services via application ServiceProviders.
+// This application is launched by share_echo.js. It both provides
+// and requests an EchoService implementation.
+//
+define("main", [
+  "console",
+  "mojo/services/public/js/application",
+  "examples/echo/echo_service.mojom",
+], function(console, application, echo) {
+
+  var Application = application.Application;
+  var EchoService = echo.EchoService;
+
+  class EchoServiceImpl {
+    echoString(s) {
+      return Promise.resolve({value: "ShareEchoTarget: " + s});
+    }
+  }
+
+  class ShareEchoTarget extends Application {
+    acceptConnection(initiatorURL, shareEchoSP) {
+      // The shareEchoSP parameter is-a JS ServiceProvider that's
+      // connected to the share_echo.js application. We can request the
+      // share_echo.js implementation of EchoService and provide the
+      // share_echo.js application with our own EchoService implementation.
+      var echoService = shareEchoSP.requestService(EchoService);
+      echoService.echoString("ShareEchoTarget").then(function(response) {
+        console.log(response.value);
+      });
+      shareEchoSP.provideService(EchoService, EchoServiceImpl);
+    }
+  }
+
+  return ShareEchoTarget;
+});