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/rw_lock_wrapper.h

@@ -0,0 +1,66 @@
+/*
+ *  Copyright (c) 2011 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.
+ */
+
+#ifndef RTC_BASE_SYNCHRONIZATION_RW_LOCK_WRAPPER_H_
+#define RTC_BASE_SYNCHRONIZATION_RW_LOCK_WRAPPER_H_
+
+#include "rtc_base/thread_annotations.h"
+
+// Note, Windows pre-Vista version of RW locks are not supported natively. For
+// these OSs regular critical sections have been used to approximate RW lock
+// functionality and will therefore have worse performance.
+
+namespace webrtc {
+
+class RTC_LOCKABLE RWLockWrapper {
+ public:
+  static RWLockWrapper* CreateRWLock();
+  virtual ~RWLockWrapper() {}
+
+  virtual void AcquireLockExclusive() RTC_EXCLUSIVE_LOCK_FUNCTION() = 0;
+  virtual void ReleaseLockExclusive() RTC_UNLOCK_FUNCTION() = 0;
+
+  virtual void AcquireLockShared() RTC_SHARED_LOCK_FUNCTION() = 0;
+  virtual void ReleaseLockShared() RTC_UNLOCK_FUNCTION() = 0;
+};
+
+// RAII extensions of the RW lock. Prevents Acquire/Release missmatches and
+// provides more compact locking syntax.
+class RTC_SCOPED_LOCKABLE ReadLockScoped {
+ public:
+  explicit ReadLockScoped(RWLockWrapper& rw_lock)
+      RTC_SHARED_LOCK_FUNCTION(rw_lock)
+      : rw_lock_(rw_lock) {
+    rw_lock_.AcquireLockShared();
+  }
+
+  ~ReadLockScoped() RTC_UNLOCK_FUNCTION() { rw_lock_.ReleaseLockShared(); }
+
+ private:
+  RWLockWrapper& rw_lock_;
+};
+
+class RTC_SCOPED_LOCKABLE WriteLockScoped {
+ public:
+  explicit WriteLockScoped(RWLockWrapper& rw_lock)
+      RTC_EXCLUSIVE_LOCK_FUNCTION(rw_lock)
+      : rw_lock_(rw_lock) {
+    rw_lock_.AcquireLockExclusive();
+  }
+
+  ~WriteLockScoped() RTC_UNLOCK_FUNCTION() { rw_lock_.ReleaseLockExclusive(); }
+
+ private:
+  RWLockWrapper& rw_lock_;
+};
+
+}  // namespace webrtc
+
+#endif  // RTC_BASE_SYNCHRONIZATION_RW_LOCK_WRAPPER_H_