Make it possible for SkyShell embedders to register services

sky/apk/demo/BUILD.gn

 # Copyright 2015 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.
 
 assert(is_android)
 
 import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 import("//sky/apk/rules.gni")
 
 android_library("java") {
-  java_files = [ "org/domokit/sky/demo/SkyDemoActivity.java" ]
+  java_files = [
+    "org/domokit/sky/demo/SkyDemoActivity.java",
+    "org/domokit/sky/demo/SkyDemoApplication.java",
+  ]
 
   deps = [
+    "//base:base_java",
+    "//mojo/public/java:bindings",
+    "//mojo/public/java:system",
+    "//sky/services/sensors",
+    "//sky/services/sensors:interfaces_java",
     "//sky/shell:java",
   ]
 }
 
 sky_apk("demo") {
   apk_name = "SkyDemo"
   android_manifest = "AndroidManifest.xml"
   deps = [
     ":java",
   ]
 }