Add the "testonly" flag to the GN test target.

build/config/android/internal_rules.gni

 # 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.
 
 import("//build/config/android/config.gni")
 
 assert(is_android)
 
 
 rebased_android_sdk = rebase_path(android_sdk, root_build_dir)
@@ skipping 61 matching lines @@
   assert(type == "android_apk" || type == "android_library" || type == "android_resources")
 
   action(target_name) {
     script = "//build/android/gyp/write_build_config.py"
     depfile = "$target_gen_dir/$target_name.d"
 
     deps = []
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
+    if (defined(invoker.testonly)) {
+      testonly = invoker.testonly
+    }
 
     outputs = [
       depfile,
       build_config
     ]
 
     possible_deps_configs = []
     foreach(d, deps) {
       dep_gen_dir = get_label_info(d, "target_gen_dir")
       dep_name = get_label_info(d, "name")
@@ skipping 579 matching lines @@
       "--dest", rebase_path(invoker.dest, root_build_dir),
     ]
     if (defined(invoker.args)) {
       args += invoker.args
     }
     if (defined(invoker.clear_dir) && invoker.clear_dir) {
       args += ["--clear"]
     }
   }
 }