Update code to current Chromium master

This corresponds to:

Chromium: 6555f9456074c0c0e5f7713564b978588ac04a5d
webrtc: c8b569e0a7ad0b369e15f0197b3a558699ec8efa

webrtc/system_wrappers/include/rw_lock_wrapper.h

@@ -0,0 +1,68 @@
+/*
+ *  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 WEBRTC_SYSTEM_WRAPPERS_INCLUDE_RW_LOCK_WRAPPER_H_
+#define WEBRTC_SYSTEM_WRAPPERS_INCLUDE_RW_LOCK_WRAPPER_H_
+
+#include "webrtc/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 LOCKABLE RWLockWrapper {
+ public:
+  static RWLockWrapper* CreateRWLock();
+  virtual ~RWLockWrapper() {}
+
+  virtual void AcquireLockExclusive() EXCLUSIVE_LOCK_FUNCTION() = 0;
+  virtual void ReleaseLockExclusive() UNLOCK_FUNCTION() = 0;
+
+  virtual void AcquireLockShared() SHARED_LOCK_FUNCTION() = 0;
+  virtual void ReleaseLockShared() UNLOCK_FUNCTION() = 0;
+};
+
+// RAII extensions of the RW lock. Prevents Acquire/Release missmatches and
+// provides more compact locking syntax.
+class SCOPED_LOCKABLE ReadLockScoped {
+ public:
+  ReadLockScoped(RWLockWrapper& rw_lock) SHARED_LOCK_FUNCTION(rw_lock)
+      : rw_lock_(rw_lock) {
+    rw_lock_.AcquireLockShared();
+  }
+
+  ~ReadLockScoped() UNLOCK_FUNCTION() {
+    rw_lock_.ReleaseLockShared();
+  }
+
+ private:
+  RWLockWrapper& rw_lock_;
+};
+
+class SCOPED_LOCKABLE WriteLockScoped {
+ public:
+  WriteLockScoped(RWLockWrapper& rw_lock) EXCLUSIVE_LOCK_FUNCTION(rw_lock)
+      : rw_lock_(rw_lock) {
+    rw_lock_.AcquireLockExclusive();
+  }
+
+  ~WriteLockScoped() UNLOCK_FUNCTION() {
+    rw_lock_.ReleaseLockExclusive();
+  }
+
+ private:
+  RWLockWrapper& rw_lock_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_RW_LOCK_WRAPPER_H_