Remove voe::OutputMixer and AudioConferenceMixer.

modules/BUILD.gn

 # Copyright (c) 2016 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("audio_coding/audio_coding.gni")
 
 group("modules") {
   public_deps = [
     "audio_coding",
-    "audio_conference_mixer",
     "audio_device",
     "audio_mixer",
     "audio_processing",
     "bitrate_controller",
     "congestion_controller",
     "desktop_capture",
     "media_file",
     "pacing",
     "remote_bitrate_estimator",
     "rtp_rtcp",
@@ skipping 199 matching lines @@
 
     if (!build_with_chromium && is_clang) {
       # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
 
     deps = [
       ":module_api",
       "../test:test_main",
       "audio_coding:audio_coding_unittests",
-      "audio_conference_mixer:audio_conference_mixer_unittests",
       "audio_device:audio_device_unittests",
       "audio_mixer:audio_mixer_unittests",
       "audio_processing:audio_processing_unittests",
       "bitrate_controller:bitrate_controller_unittests",
       "congestion_controller:congestion_controller_unittests",
       "desktop_capture:desktop_capture_unittests",
       "media_file:media_file_unittests",
       "pacing:pacing_unittests",
       "remote_bitrate_estimator:remote_bitrate_estimator_unittests",
       "rtp_rtcp:rtp_rtcp_unittests",
@@ skipping 13 matching lines @@
       shard_timeout = 900
     }
     if (is_ios) {
       info_plist = "../test/ios/Info.plist"
       deps += [ ":modules_unittests_bundle_data" ]
       configs += [ "..:common_objc" ]
       ldflags = [ "-ObjC" ]
     }
   }
 }