Fix more disabled MSVC warnings, base/ edition.

base/numerics/safe_math.h

 // Copyright 2014 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 BASE_SAFE_MATH_H_
 #define BASE_SAFE_MATH_H_
 
 #include "base/numerics/safe_math_impl.h"
 
 namespace base {
@@ skipping 187 matching lines @@
       const CheckedNumeric<T>& lhs, const CheckedNumeric<T>& rhs) {           \
     typedef typename ArithmeticPromotion<T>::type Promotion;                  \
     /* Floating point always takes the fast path */                           \
     if (std::numeric_limits<T>::is_iec559)                                    \
       return CheckedNumeric<T>(lhs.ValueUnsafe() OP rhs.ValueUnsafe());       \
     if (IsIntegerArithmeticSafe<Promotion, T, T>::value)                      \
       return CheckedNumeric<Promotion>(                                       \
           lhs.ValueUnsafe() OP rhs.ValueUnsafe(),                             \
           GetRangeConstraint(rhs.validity() | lhs.validity()));               \
     RangeConstraint validity = RANGE_VALID;                                   \
-    T result = Checked##NAME(static_cast<Promotion>(lhs.ValueUnsafe()),       \
-                             static_cast<Promotion>(rhs.ValueUnsafe()),       \
-                             &validity);                                      \
+    T result = static_cast<T>(Checked##NAME(                                  \
+        static_cast<Promotion>(lhs.ValueUnsafe()),                            \
+        static_cast<Promotion>(rhs.ValueUnsafe()),                            \
+        &validity));                                                          \
     return CheckedNumeric<Promotion>(                                         \
         result,                                                               \
         GetRangeConstraint(validity | lhs.validity() | rhs.validity()));      \
   }                                                                           \
   /* Assignment arithmetic operator implementation from CheckedNumeric. */    \
   template <typename T>                                                       \
   template <typename Src>                                                     \
   CheckedNumeric<T>& CheckedNumeric<T>::operator COMPOUND_OP(Src rhs) {       \
     *this = CheckedNumeric<T>::cast(*this) OP CheckedNumeric<Src>::cast(rhs); \
     return *this;                                                             \
@@ skipping 41 matching lines @@
 
 #undef BASE_NUMERIC_ARITHMETIC_OPERATORS
 
 }  // namespace internal
 
 using internal::CheckedNumeric;
 
 }  // namespace base
 
 #endif  // BASE_SAFE_MATH_H_