[Cronet] Use gn desc deps to find third_party licenses.

BUILD.gn

 # Copyright (c) 2013 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.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 229 matching lines @@
       "//ios/chrome/common",
       "//ios/net:ios_net_unittests",
       "//ios/public/provider/chrome/browser",
       "//ios/public/provider/web",
       "//ios/testing:ocmock_support_unittest",
       "//ios/third_party/earl_grey",
       "//ios/web:ios_web_inttests",
       "//ios/web:ios_web_unittests",
       "//ios/web/shell:ios_web_shell",
     ]
+
+    if (!is_component_build) {
+      deps += [ "//components/cronet/ios:cronet_package" ]
+    }
   }
 
   deps += root_extra_deps
 
   if (enable_extensions) {
     deps += [ "//extensions/shell:app_shell_unittests" ]
   }
 
   if (enable_media_router) {
     deps += [ "//chrome/browser/media/router" ]
@@ skipping 698 matching lines @@
   assert(target_name != "")  # Mark as used.
   sources = invoker.actual_sources
   assert(
       sources == invoker.actual_sources,
       "Do not use a platform name in your output directory (found \"$root_build_dir\"). http://crbug.com/548283")
 }
 
 assert_valid_out_dir("_unused") {
   actual_sources = [ "$root_build_dir/foo" ]
 }