Mark gtest and gmock as testonly in GN.

media/audio/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("//media/media_options.gni")
 
 # When libpulse is not directly linked, use stubs to allow for dlopening of the
 # binary.
 if (!linux_link_pulseaudio) {
   action("pulse_generate_stubs") {
@@ skipping 218 matching lines @@
     } else {
       # TODO(ajwong): Technically, this dl should go in the action.
       libs += [ "dl" ]
       deps += [ ":pulse_generate_stubs" ]
       sources += get_target_outputs(":pulse_generate_stubs")
     }
   }
 }
 
 source_set("test_support") {
+  testonly = true
   sources = [
     "clockless_audio_sink.cc",
     "clockless_audio_sink.h",
     "mock_audio_manager.cc",
     "mock_audio_manager.h",
     "mock_audio_source_callback.cc",
     "mock_audio_source_callback.h",
     "test_audio_input_controller_factory.cc",
     "test_audio_input_controller_factory.h",
   ]
   deps = [ "//testing/gmock" ]
   configs += [ "//media:media_config" ]
 }
 
 source_set("unittests") {
+  testonly = true
   sources = [
     "audio_input_controller_unittest.cc",
     "audio_input_unittest.cc",
     "audio_low_latency_input_output_unittest.cc",
     "audio_manager_unittest.cc",
     "audio_output_controller_unittest.cc",
     "audio_output_device_unittest.cc",
     "audio_output_proxy_unittest.cc",
     "audio_parameters_unittest.cc",
     "audio_power_monitor_unittest.cc",
@@ skipping 53 matching lines @@
       "win/core_audio_util_win_unittest.cc",
     ]
   }
 
   if (use_alsa) {
     sources += [
       "alsa/alsa_output_unittest.cc",
     ]
   }
 }