Update code to current Chromium master

This corresponds to:

Chromium: 6555f9456074c0c0e5f7713564b978588ac04a5d
webrtc: c8b569e0a7ad0b369e15f0197b3a558699ec8efa

webrtc/system_wrappers/include/sleep.h

@@ -0,0 +1,24 @@
+/*
+ *  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.
+ */
+// An OS-independent sleep function.
+
+#ifndef WEBRTC_SYSTEM_WRAPPERS_INCLUDE_SLEEP_H_
+#define WEBRTC_SYSTEM_WRAPPERS_INCLUDE_SLEEP_H_
+
+namespace webrtc {
+
+// This function sleeps for the specified number of milliseconds.
+// It may return early if the thread is woken by some other event,
+// such as the delivery of a signal on Unix.
+void SleepMs(int msecs);
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_SLEEP_H_