Delete Timing class, timing.h, and update all users.

webrtc/base/timeutils.h

 /*
  *  Copyright 2005 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.
  */
 
@@ skipping 90 matching lines @@
  private:
   uint32_t last_ts_;
   int64_t num_wrap_;
 };
 
 // Convert from std::tm, which is relative to 1900-01-01 00:00 to number of
 // seconds from 1970-01-01 00:00 ("epoch").  Don't return time_t since that
 // is still 32 bits on many systems.
 int64_t TmToSeconds(const std::tm& tm);
 
+// Returns number of microseconds since January 1, 1970, UTC.

[hbos, 2016/09/08 07:50:43]

Comment about it being the wall clock and that it could change, e.g. not
monotonically increasing, don't use for measuring time between two calls.

[nisse-webrtc, 2016/09/08 09:07:14]

I've added a comment on proper and improper use.

+int64_t TimeUTCMicros();
+
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_TIMEUTILS_H_