Make it possible to run Sky apps offline

sky/shell/dart/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.
+
+source_set("dart") {
+  sources = [
+    "dart_library_provider_files.cc",
+    "dart_library_provider_files.h",
+    "dart_library_provider_network.cc",
+    "dart_library_provider_network.h",
+  ]
+
+  deps = [
+    "//base",
+    "//build/config/sanitizers:deps",
+    "//dart/runtime:libdart",
+    "//mojo/common",
+    "//mojo/public/cpp/application",
+    "//mojo/services/network/public/interfaces",
+    "//sky/engine/tonic",
+    "//sky/engine/wtf",
+    "//url",
+  ]
+}