Update to current webrtc library

This is from the upstream library commit id
3326535126e435f1ba647885ce43a8f0f3d317eb, corresponding to Chromium
88.0.4290.1.

webrtc/rtc_base/synchronization/BUILD.gn

@@ -0,0 +1,138 @@
+# Copyright (c) 2018 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) {
+  import("//build/config/android/config.gni")
+  import("//build/config/android/rules.gni")
+}
+
+rtc_library("yield") {
+  sources = [
+    "yield.cc",
+    "yield.h",
+  ]
+  deps = []
+}
+
+rtc_library("mutex") {
+  sources = [
+    "mutex.cc",
+    "mutex.h",
+    "mutex_critical_section.h",
+    "mutex_pthread.h",
+  ]
+  if (rtc_use_absl_mutex) {
+    sources += [ "mutex_abseil.h" ]
+  }
+
+  deps = [
+    ":yield",
+    "..:checks",
+    "..:macromagic",
+    "..:platform_thread_types",
+    "../system:unused",
+  ]
+  absl_deps = [ "//third_party/abseil-cpp/absl/base:core_headers" ]
+  if (rtc_use_absl_mutex) {
+    absl_deps += [ "//third_party/abseil-cpp/absl/synchronization" ]
+  }
+}
+
+rtc_library("rw_lock_wrapper") {
+  public = [ "rw_lock_wrapper.h" ]
+  sources = [ "rw_lock_wrapper.cc" ]
+  deps = [ "..:macromagic" ]
+  if (is_win) {
+    sources += [
+      "rw_lock_win.cc",
+      "rw_lock_win.h",
+    ]
+    deps += [ "..:logging" ]
+  } else {
+    sources += [
+      "rw_lock_posix.cc",
+      "rw_lock_posix.h",
+    ]
+  }
+}
+
+rtc_library("sequence_checker") {
+  sources = [
+    "sequence_checker.cc",
+    "sequence_checker.h",
+  ]
+  deps = [
+    ":mutex",
+    "..:checks",
+    "..:criticalsection",
+    "..:macromagic",
+    "..:platform_thread_types",
+    "..:stringutils",
+    "../../api/task_queue",
+    "../system:rtc_export",
+  ]
+}
+
+rtc_library("yield_policy") {
+  sources = [
+    "yield_policy.cc",
+    "yield_policy.h",
+  ]
+  deps = [ "..:checks" ]
+  absl_deps = [
+    "//third_party/abseil-cpp/absl/base:config",
+    "//third_party/abseil-cpp/absl/base:core_headers",
+  ]
+}
+
+if (rtc_include_tests) {
+  rtc_library("synchronization_unittests") {
+    testonly = true
+    sources = [
+      "mutex_unittest.cc",
+      "yield_policy_unittest.cc",
+    ]
+    deps = [
+      ":mutex",
+      ":yield",
+      ":yield_policy",
+      "..:checks",
+      "..:macromagic",
+      "..:rtc_base",
+      "..:rtc_event",
+      "../../test:test_support",
+      "//third_party/google_benchmark",
+    ]
+  }
+
+  rtc_library("mutex_benchmark") {
+    testonly = true
+    sources = [ "mutex_benchmark.cc" ]
+    deps = [
+      ":mutex",
+      "../system:unused",
+      "//third_party/google_benchmark",
+    ]
+  }
+
+  rtc_library("sequence_checker_unittests") {
+    testonly = true
+
+    sources = [ "sequence_checker_unittest.cc" ]
+    deps = [
+      ":sequence_checker",
+      "..:checks",
+      "..:rtc_base_approved",
+      "..:task_queue_for_test",
+      "../../api:function_view",
+      "../../test:test_main",
+      "../../test:test_support",
+    ]
+  }
+}