Cleanup some constexpr nits in base/numerics

base/numerics/safe_math_impl.h

Index: base/numerics/safe_math_impl.h
diff --git a/base/numerics/safe_math_impl.h b/base/numerics/safe_math_impl.h
index eeda234796ec179f034121e9385259e7cd4c6b4a..77a9b0ba3c8b0395da0a630efc137a640fc73856 100644
--- a/base/numerics/safe_math_impl.h
+++ b/base/numerics/safe_math_impl.h
@@ -115,7 +115,7 @@ struct UnsignedOrFloatForSize<Numeric, false, true> {
 // Helper templates for integer manipulations.
 
 template <typename T>
-bool HasSignBit(T x) {
+constexpr bool HasSignBit(T x) {
   // Cast to unsigned since right shift on signed is undefined.
   return !!(static_cast<typename UnsignedIntegerForSize<T>::type>(x) >>
             PositionOfSignBit<T>::value);
@@ -123,7 +123,7 @@ bool HasSignBit(T x) {
 
 // This wrapper undoes the standard integer promotions.
 template <typename T>
-T BinaryComplement(T x) {
+constexpr T BinaryComplement(T x) {
   return static_cast<T>(~x);
 }