Fix Chromium style checker warnings for MockAudioDecoder

webrtc/test/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../webrtc.gni")
 import("//build/config/ui.gni")
@@ skipping 563 matching lines @@
     "../base:rtc_base_approved",
     "../common_video",
     "../modules/media_file",
     "//testing/gtest",
   ]
 }
 
 rtc_source_set("audio_codec_mocks") {
   testonly = true
   sources = [
+    "mock_audio_decoder.cc",
     "mock_audio_decoder.h",
     "mock_audio_decoder_factory.h",
     "mock_audio_encoder.cc",
     "mock_audio_encoder.h",
     "mock_audio_encoder_factory.h",
   ]
 
   deps = [
     ":test_support",
     "../api/audio_codecs:audio_codecs_api",
     "../api/audio_codecs:builtin_audio_decoder_factory",
     "../base:rtc_base_approved",
     "//testing/gmock",
   ]
 }
 
 if (!build_with_chromium && is_android) {
   android_library("native_test_java") {
     testonly = true
     java_files = [
       "android/org/webrtc/native_test/RTCNativeUnitTest.java",
       "android/org/webrtc/native_test/RTCNativeUnitTestActivity.java",
     ]
     deps = [
       "//testing/android/native_test:native_test_java",
       "//webrtc/base:base_java",
     ]
   }
 }