Use fake clock in some more networks tests.

webrtc/base/fakeclock.h

 /*
  *  Copyright 2016 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 38 matching lines @@
 // unsets it in its destructor.
 class ScopedFakeClock : public FakeClock {
  public:
   ScopedFakeClock();
   ~ScopedFakeClock() override;
 
  private:
   ClockInterface* prev_clock_;
 };
 
+// Helper class to "undo" the fake clock temporarily.
+class ScopedRealClock {
+ public:
+  ScopedRealClock();
+  ~ScopedRealClock();
+
+ private:
+  ClockInterface* prev_clock_;
+};
+
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_FAKECLOCK_H_