Upstream various ios/web utilities and helpers

ios/web/navigation/time_smoother.h

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef IOS_WEB_NAVIGATION_TIME_SMOOTHER_H_
+#define IOS_WEB_NAVIGATION_TIME_SMOOTHER_H_
+
+#include "base/time/time.h"
+
+namespace web {
+
+// Helper class to smooth out runs of duplicate timestamps while still
+// allowing time to jump backwards.
+//
+// Duplicated from NavigationControllerImpl (until we have a better
+// idea how to handle NavigationController implementation overlap
+// in general).
+class TimeSmoother {
+ public:
+  // Returns |t| with possibly some time added on.
+  base::Time GetSmoothedTime(base::Time t);
+
+ private:
+  // |low_water_mark_| is the first time in a sequence of adjusted
+  // times and |high_water_mark_| is the last.
+  base::Time low_water_mark_;
+  base::Time high_water_mark_;
+};
+
+}  // namespace web
+
+#endif  // IOS_WEB_NAVIGATION_TIME_SMOOTHER_H_