Add browser_tests to the GN build.

device/serial/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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 # GYP version: device/serial/serial.gyp:device_serial
 static_library("serial") {
   output_name = "device_serial"
 
@@ skipping 34 matching lines @@
     ":serial_mojo",
   ]
   deps = []
 
   if (is_linux) {
     deps += [ "//device/udev_linux" ]
   }
 }
 
 # GYP version: device/serial/serial.gyp:device_serial_test_util
-static_library("test_util") {
-  output_name = "device_serial_test_util"
-
+static_library("test_support") {
   sources = [
     "test_serial_io_handler.cc",
     "test_serial_io_handler.h",
   ]
 
   deps = [
     ":serial",
   ]
 }
 
 # GYP version: device/serial/serial.gyp:device_serial_mojo
 mojom("serial_mojo") {
   visibility = [
     ":serial",
     "//extensions:extensions_renderer_resources_grit",
   ]
 
   sources = [
     "data_stream.mojom",
     "data_stream_serialization.mojom",
     "serial.mojom",
     "serial_serialization.mojom",
   ]
 }