Add gfx::ToRoundedInt safe conversion method from float to int.

ui/gfx/safe_floor_ceil.cc

-// Copyright (c) 2012 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 <cmath>
-#include <limits>
-
-namespace gfx {
-
-int ClampToInt(float value) {
-  if (value != value)
-     return 0; // no int NaN.
-  if (value > std::numeric_limits<int>::max())
-    return std::numeric_limits<int>::max();
-  if (value < std::numeric_limits<int>::min())
-    return std::numeric_limits<int>::min();
-  return static_cast<int>(value);
-}
-
-int ToFlooredInt(float value) {
-  return ClampToInt(std::floor(value));
-}
-
-int ToCeiledInt(float value) {
-  return ClampToInt(std::ceil(value));
-}
-
-}  // namespace gfx
-