Move SaturatedArithmetic from Blink to base

ui/gfx/geometry/safe_integer_conversions.h

 // 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.
 
 #ifndef UI_GFX_GEOMETRY_SAFE_INTEGER_CONVERSIONS_H_
 #define UI_GFX_GEOMETRY_SAFE_INTEGER_CONVERSIONS_H_
 
 #include <cmath>
 #include <limits>
 
@@ skipping 39 matching lines @@
 inline bool IsExpressibleAsInt(float value) {
   if (value != value)
     return false; // no int NaN.
   if (value > std::numeric_limits<int>::max())
     return false;
   if (value < std::numeric_limits<int>::min())
     return false;
   return true;
 }
 
-// Returns true iff a+b would overflow max int.
-constexpr bool AddWouldOverflow(int a, int b) {
-  // In this function, GCC tries to make optimizations that would only
-  // work if max - a wouldn't overflow but it isn't smart enough to notice that
-  // a > 0.  So cast everything to unsigned to avoid this.  As it is guaranteed
-  // that max - a and b are both already positive, the cast is a noop.
-  //
-  // This is intended to be: a > 0 && max - a < b
-  return a > 0 && b > 0 &&
-         static_cast<unsigned>(std::numeric_limits<int>::max() - a) <
-             static_cast<unsigned>(b);
-}
-
-// Returns true iff a+b would underflow min int.
-constexpr bool AddWouldUnderflow(int a, int b) {
-  return a < 0 && b < std::numeric_limits<int>::min() - a;
-}
-
-// Returns true iff a-b would overflow max int.
-constexpr bool SubtractWouldOverflow(int a, int b) {
-  return b < 0 && a > std::numeric_limits<int>::max() + b;
-}
-
-// Returns true iff a-b would underflow min int.
-constexpr bool SubtractWouldUnderflow(int a, int b) {
-  return b > 0 && a < std::numeric_limits<int>::min() + b;
-}
-
-// Safely adds a+b without integer overflow/underflow.  Exceeding these
-// bounds will clamp to the max or min int limit.
-constexpr int SafeAdd(int a, int b) {
-  return AddWouldOverflow(a, b)
-             ? std::numeric_limits<int>::max()
-             : AddWouldUnderflow(a, b) ? std::numeric_limits<int>::min()
-                                       : a + b;
-}
-
-// Safely subtracts a-b without integer overflow/underflow.  Exceeding these
-// bounds will clamp to the max or min int limit.
-constexpr int SafeSubtract(int a, int b) {
-  return SubtractWouldOverflow(a, b)
-             ? std::numeric_limits<int>::max()
-             : SubtractWouldUnderflow(a, b) ? std::numeric_limits<int>::min()
-                                            : a - b;
-}
-
 }  // namespace gfx
 
 #endif  // UI_GFX_GEOMETRY_SAFE_INTEGER_CONVERSIONS_H_