Upstream various ios/web utilities and helpers

ios/web/navigation/time_smoother.cc

+// 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.
+
+#include "ios/web/navigation/time_smoother.h"
+
+namespace web {
+
+// Duplicated from content/browser/web_contents/navigation_controller_impl.cc.
+base::Time TimeSmoother::GetSmoothedTime(base::Time t) {
+  // If |t| is between the water marks, we're in a run of duplicates
+  // or just getting out of it, so increase the high-water mark to get
+  // a time that probably hasn't been used before and return it.
+  if (low_water_mark_ <= t && t <= high_water_mark_) {
+    high_water_mark_ += base::TimeDelta::FromMicroseconds(1);
+    return high_water_mark_;
+  }
+
+  // Otherwise, we're clear of the last duplicate run, so reset the
+  // water marks.
+  low_water_mark_ = high_water_mark_ = t;
+  return t;
+}
+
+}  // namespace web