Make it possible for SkyShell embedders to register services

sky/shell/BUILD.gn

Index: sky/shell/BUILD.gn
diff --git a/sky/shell/BUILD.gn b/sky/shell/BUILD.gn
index d583784cf03ac41d3bac7a24b2a3e05da4dc458f..86f6e043a8d464f8426088afc472826262b392ee 100644
--- a/sky/shell/BUILD.gn
+++ b/sky/shell/BUILD.gn
@@ -75,6 +75,8 @@ android_library("java") {
     "org/domokit/sky/shell/GestureProvider.java",
     "org/domokit/sky/shell/JavaServiceProvider.java",
     "org/domokit/sky/shell/PlatformView.java",
+    "org/domokit/sky/shell/ServiceFactory.java",
+    "org/domokit/sky/shell/ServiceRegistry.java",
     "org/domokit/sky/shell/SkyActivity.java",
     "org/domokit/sky/shell/SkyApplication.java",
     "org/domokit/sky/shell/SkyMain.java",
@@ -88,8 +90,6 @@ android_library("java") {
     "//mojo/public/java:system",
     "//mojo/services/network/public/interfaces:interfaces_java",
     "//sky/services/oknet",
-    "//sky/services/sensors",
-    "//sky/services/sensors:interfaces_java",
     "//sky/services/viewport:viewport_java",
   ]
 }