mojo: Update content handler API

mojo/apps/js/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 group("js") {
   # Meta-target, don't link into production code.
   testonly = true
   deps = [
     ":js_content_handler",
-    ":js_standalone"
   ]
 }
 
 source_set("mojo_runner") {
   sources = [
     "mojo_runner_delegate.cc",
     "mojo_runner_delegate.h",
   ]
 
   public_deps = [
     "//mojo/bindings/js",
   ]
   deps = [
     "//base",
     "//gin",
     "//mojo/apps/js/bindings",
     "//mojo/apps/js/bindings/gl",
     "//v8",
   ]
 }
 
 source_set("js_apps") {
   sources = [
-    "application_delegate_impl.cc",
     "js_app.cc",
     "mojo_bridge_module.cc",
   ]
 
   public_deps = [
     "//mojo/bindings/js",
   ]
   deps = [
     ":mojo_runner",
     "//mojo/application",
     "//mojo/public/c/system:for_shared_library",
     "//mojo/public/cpp/utility",
   ]
 }
 
 shared_library("js_content_handler") {
   sources = [
-    "content_handler_impl.cc",
     "content_handler_main.cc",
   ]
 
   deps = [
     ":js_apps",
     "//base:i18n",
     "//mojo/application:application",
+    "//mojo/application:content_handler",
     "//mojo/environment:chromium",
     "//mojo/services/public/interfaces/content_handler",
   ]
 }
-
-shared_library("js_standalone") {
-  sources = [
-    "standalone_main.cc"
-  ]
-
-  deps = [
-    ":js_apps",
-    "//base:i18n",
-    "//mojo/application:application",
-    "//mojo/environment:chromium",
-    "//mojo/public/cpp/application",
-  ]
-}
-
-
-