Cleanup sign checking in safe math code

base/numerics/safe_conversions_impl.h

Index: base/numerics/safe_conversions_impl.h
diff --git a/base/numerics/safe_conversions_impl.h b/base/numerics/safe_conversions_impl.h
index ef5adf0bf9ab49f9df9a5e5d80a2c3b08b9fe707..79dee83e85a00fcc66ff141a74f6b27269cb0d27 100644
--- a/base/numerics/safe_conversions_impl.h
+++ b/base/numerics/safe_conversions_impl.h
@@ -290,11 +290,6 @@ struct TwiceWiderInteger {
                                        IsSigned>::type;
 };
 
-template <typename Integer>
-struct PositionOfSignBit {
-  static const size_t value = IntegerBitsPlusSign<Integer>::value - 1;
-};
-
 enum ArithmeticPromotionCategory {
   LEFT_PROMOTION,  // Use the type of the left-hand argument.
   RIGHT_PROMOTION  // Use the type of the right-hand argument.