Split audio mixer into interface and implementation.

webrtc/api/BUILD.gn

 # Copyright (c) 2015 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("../build/webrtc.gni")
 if (is_android) {
@@ skipping 298 matching lines @@
     "stats/rtcstats.h",
     "stats/rtcstats_objects.h",
     "stats/rtcstatsreport.h",
   ]
 
   deps = [
     "../base:rtc_base_approved",
   ]
 }
 
+# GYP version: webrtc/api/api.gyp:audio_mixer_api
+rtc_source_set("audio_mixer_api") {
+  sources = [
+    "audio/audio_mixer.h",
+  ]
+
+  deps = [
+    "../base:rtc_base_approved",
+  ]
+}
+
 if (rtc_include_tests) {
   config("peerconnection_unittests_config") {
     # The warnings below are enabled by default. Since GN orders compiler flags
     # for a target before flags from configs, the only way to disable such
     # warnings is by having them in a separate config, loaded from the target.
     # TODO(kjellander): Make the code compile without disabling these flags.
     # See https://bugs.webrtc.org/3307.
     if (is_clang && is_win) {
       cflags = [
         # See https://bugs.chromium.org/p/webrtc/issues/detail?id=6267
@@ skipping 136 matching lines @@
 
       shared_libraries = [ ":libjingle_peerconnection_so" ]
     }
 
     android_resources("libjingle_peerconnection_android_unittest_resources") {
       resource_dirs = [ "androidtests/res" ]
       custom_package = "org.webrtc"
     }
   }
 }