Support GCM ciphers even if ENABLE_EXTERNAL_AUTH is defined.

webrtc/pc/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")
 if (is_android) {
@@ skipping 37 matching lines @@
     "srtpfilter.h",
     "voicechannel.h",
   ]
 
   deps = [
     "../api:call_api",
     "../base:rtc_base",
     "../media",
   ]
 
-  if (build_with_chromium) {
+  if (rtc_enable_external_auth) {
     sources += [
       "externalhmac.cc",
       "externalhmac.h",
     ]
   }
   if (rtc_build_libsrtp) {
     deps += [ "//third_party/libsrtp" ]
   }
 
   public_configs = [ ":rtc_pc_config" ]
@@ skipping 292 matching lines @@
       "//testing/gmock",
     ]
 
     if (is_android) {
       deps += [ "//testing/android/native_test:native_test_support" ]
 
       shard_timeout = 900
     }
   }
 }