Separate building and enabling libevent.

webrtc/build/webrtc.gni

 # 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("//build/config/arm.gni")
 import("//build/config/features.gni")
@@ skipping 41 matching lines @@
   rtc_enable_android_opensl = false
 
   # Link-Time Optimizations.
   # Executes code generation at link-time instead of compile-time.
   # https://gcc.gnu.org/wiki/LinkTimeOptimization
   rtc_use_lto = false
 
   rtc_include_tests = false
   rtc_restrict_logging = true
 
+  # Enable libevent task queues on platforms that support it.
+  if (is_win || is_mac || is_ios || is_nacl) {
+    rtc_enable_libevent = false
+    rtc_build_libevent = false
+  } else {
+    rtc_enable_libevent = true
+    rtc_build_libevent = true
+  }
+
   if (is_ios) {
     rtc_build_libjpeg = false
     rtc_enable_protobuf = false
   }
 
   if (current_cpu == "arm" || current_cpu == "arm64") {
     rtc_prefer_fixed_point = true
   }
 
   # TODO(ljubomir): Unset rtc_use_openmax_dl for mips64el once mips64el gets
@@ skipping 37 matching lines @@
 declare_args() {
   # Include the iLBC audio codec?
   rtc_include_ilbc = !(build_with_chromium || build_with_mozilla)
 }
 
 # Make it possible to provide custom locations for some libraries (move these
 # up into declare_args should we need to actually use them for the GN build).
 rtc_libvpx_dir = "//third_party/libvpx"
 rtc_libyuv_dir = "//third_party/libyuv"
 rtc_opus_dir = "//third_party/opus"