Re-land "Add GN build targets for the rest of mojo/public"

mojo/public/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("mojo") {
+group("public") {
   deps = [
+    "//mojo/public/c/system",
+    "//mojo/public/cpp/application",
     "//mojo/public/cpp/bindings",
+    "//mojo/public/cpp/environment:standalone",
+    "//mojo/public/cpp/utility",
     "//mojo/public/interfaces/bindings/tests:test_interfaces",
-    "//mojo/public/interfaces/service_provider:service_provider",
+    "//mojo/public/interfaces/service_provider",
     "//mojo/public/js/bindings",
   ]
+
+  if (is_android) {
+    deps += [
+      "//mojo/public/java",
+    ]
+  }
 }