Replace remaining gflags usages with rtc_base/flags

webrtc/modules/audio_processing/test/conversational_speech/BUILD.gn

 # Copyright (c) 2017 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/webrtc.gni")
 
 group("conversational_speech") {
   testonly = true
   deps = [
     ":conversational_speech_generator",
   ]
 }
 
 rtc_executable("conversational_speech_generator") {
   testonly = true
   sources = [
     "generator.cc",
   ]
   deps = [
     ":lib",
     "../../../../rtc_base:rtc_base_approved",
     "../../../../test:test_support",
-    "//third_party/gflags",
   ]
 }
 
 rtc_static_library("lib") {
   testonly = true
   sources = [
     "config.cc",
     "config.h",
     "multiend_call.cc",
     "multiend_call.h",
@@ skipping 26 matching lines @@
   deps = [
     ":lib",
     "../../../..:webrtc_common",
     "../../../../common_audio",
     "../../../../rtc_base:rtc_base_approved",
     "../../../../test:test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }