Run gn format on all BUILD.gn files (gn version 306668)

mojo/dart/embedder/test/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.
 
 test("dart_unittests") {
   deps = [
     "//base",
     "//crypto:crypto",
     "//mojo/dart/embedder:dart_controller",
     "//mojo/edk/test:run_all_unittests",
     "//mojo/edk/test:test_support",
     "//mojo/public/cpp/environment",
     "//mojo/public/cpp/system",
     "//mojo/public/cpp/utility",
     "//mojo/environment:chromium",
   ]
 
-  sources = [ "run_dart_tests.cc" ]
+  sources = [
+    "run_dart_tests.cc",
+  ]
 }