Reland of New task queueing primitive for async tasks: TaskQueue.

webrtc/build/common.gypi

 # Copyright (c) 2012 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.
 
 # This file contains common settings for building WebRTC components.
 
@@ skipping 23 matching lines @@
 
           ['build_with_chromium==1', {
             'webrtc_root%': '<(DEPTH)/third_party/webrtc',
             'apk_tests_path%': '<(DEPTH)/third_party/webrtc/build/apk_tests_noop.gyp',
             'modules_java_gyp_path%': '<(DEPTH)/third_party/webrtc/modules/modules_java_chromium.gyp',
           }, {
             'webrtc_root%': '<(DEPTH)/webrtc',
             'apk_tests_path%': '<(DEPTH)/webrtc/build/apk_tests.gyp',
             'modules_java_gyp_path%': '<(DEPTH)/webrtc/modules/modules_java.gyp',
           }],
+
+          # Controls whether we use libevent on posix platforms.
+          ['OS=="win" or OS=="mac" or OS=="ios"', {
+            'build_libevent%': 0,
+          }, {
+            'build_libevent%': 1,
+          }],
         ],
       },
       'build_with_chromium%': '<(build_with_chromium)',
       'build_with_mozilla%': '<(build_with_mozilla)',
+      'build_libevent%': '<(build_libevent)',
       'webrtc_root%': '<(webrtc_root)',
       'apk_tests_path%': '<(apk_tests_path)',
       'modules_java_gyp_path%': '<(modules_java_gyp_path)',
       'webrtc_vp8_dir%': '<(webrtc_root)/modules/video_coding/codecs/vp8',
       'webrtc_vp9_dir%': '<(webrtc_root)/modules/video_coding/codecs/vp9',
       'include_ilbc%': '<(include_ilbc)',
       'include_opus%': '<(include_opus)',
       'opus_dir%': '<(DEPTH)/third_party/opus',
     },
     'build_with_chromium%': '<(build_with_chromium)',
     'build_with_mozilla%': '<(build_with_mozilla)',
+    'build_libevent%': '<(build_libevent)',
     'webrtc_root%': '<(webrtc_root)',
     'apk_tests_path%': '<(apk_tests_path)',
     'test_runner_path': '<(DEPTH)/webrtc/build/android/test_runner.py',
     'modules_java_gyp_path%': '<(modules_java_gyp_path)',
     'webrtc_vp8_dir%': '<(webrtc_vp8_dir)',
     'webrtc_vp9_dir%': '<(webrtc_vp9_dir)',
     'include_ilbc%': '<(include_ilbc)',
     'include_opus%': '<(include_opus)',
     'rtc_relative_path%': 1,
     'external_libraries%': '0',
@@ skipping 241 matching lines @@
             ],
           }],
           ['clang==1', {
             'cflags': [
               '-Wimplicit-fallthrough',
               '-Wthread-safety',
             ],
           }],
         ],
       }],
+      ['build_libevent==1', {
+        'defines': [
+          'WEBRTC_BUILD_LIBEVENT',
+        ],
+      }],
       ['target_arch=="arm64"', {
         'defines': [
           'WEBRTC_ARCH_ARM64',
           'WEBRTC_HAS_NEON',
         ],
       }],
       ['target_arch=="arm"', {
         'defines': [
           'WEBRTC_ARCH_ARM',
         ],
@@ skipping 172 matching lines @@
           # For access to standard POSIXish features, use WEBRTC_POSIX instead
           # of a more specific macro.
           'defines': [
             'WEBRTC_POSIX',
           ],
         }],
       ],
     },
   }, # target_defaults
 }