Expose ability to download network service impl in SDK.

mojo/services/network/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("network") {
-  deps = [
-    ":copy_prebuilt_network_service",
-    ":copy_prebuilt_network_service_apptests",
-  ]
-}
-
-copy("copy_prebuilt_network_service") {
-  filename = "network_service.mojo"
-  if (is_android) {
-    sources = [
-      "prebuilt/android-arm/$filename",
-    ]
-  } else {
-    assert(is_linux)
-    sources = [
-      "prebuilt/linux-x64/$filename",
-    ]
-  }
-  outputs = [
-    "$root_out_dir/$filename",
-  ]
-}
-
-copy("copy_prebuilt_network_service_apptests") {
-  filename = "network_service_apptests.mojo"
-  if (is_android) {
-    sources = [
-      "prebuilt/android-arm/$filename",
-    ]
-  } else {
-    assert(is_linux)
-    sources = [
-      "prebuilt/linux-x64/$filename",
-    ]
-  }
-  outputs = [
-    "$root_out_dir/$filename",
-  ]
-}