Changes magic sequence to '!#mojo ' and strips 'mojo ' when building url

examples/js/share_echo_target.js

-#!mojo:js_content_handler
+#!mojo 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) {
 
@@ skipping 15 matching lines @@
       var echoService = shareEchoSP.requestService(EchoService);
       echoService.echoString("ShareEchoTarget").then(function(response) {
         console.log(response.value);
       });
       shareEchoSP.provideService(EchoService, EchoServiceImpl);
     }
   }
 
   return ShareEchoTarget;
 });