[Cronet] Use gn desc to find third party licenses on Android.

components/cronet/android/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.
 
 import("//build/buildflag_header.gni")
 import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 import("//build/util/process_version.gni")
 import("//build/util/version.gni")
 import("//testing/test.gni")
@@ skipping 1185 matching lines @@
                   "//net/android:net_android_java_enums_srcjar",
                   "//net/android:net_errors_java",
                 ]
   jar_path = "$_package_dir/cronet_impl_native_java-src.jar"
 }
 
 action("generate_licenses") {
   _license_path = "$_package_dir/LICENSE"
 
   script = "//components/cronet/tools/cronet_licenses.py"
+  inputs = [
+    "//build/util/LASTCHANGE",
+    "//buildtools/linux64/gn",
+  ]
   outputs = [
     _license_path,
   ]
   args = [
     "license",
     rebase_path(_license_path, root_build_dir),
+    "--gn",
+    "--gn-path",
+    rebase_path("//buildtools/linux64/gn", root_build_dir),
   ]
 }
 
 action("generate_javadoc") {
   script = "//components/cronet/tools/generate_javadoc.py"
   depfile = "$target_gen_dir/$target_name.d"
   _stamp_file = "$target_gen_dir/$target_name.stamp"
   outputs = [
     _stamp_file,
   ]
@@ skipping 260 matching lines @@
     deps = [
       ":cronet_package_copy_native_test_lib",
       ":cronet_package_copy_native_test_lib_unstripped",
       ":cronet_package_copy_test_assets",
       ":cronet_package_copy_test_files",
       ":cronet_package_copy_test_support_apks",
       ":repackage_extracted_test_jars",
     ]
   }
 }