Add Float64Round operator.

src/base/flags.h

 // Copyright 2014 the V8 project 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 V8_BASE_FLAGS_H_
 #define V8_BASE_FLAGS_H_
 
 #include "src/base/compiler-specific.h"
 
 namespace v8 {
 namespace base {
 
 // The Flags class provides a type-safe way of storing OR-combinations of enum
 // values. The Flags<T, S> class is a template class, where T is an enum type,
 // and S is the underlying storage type (usually int).
 //
 // The traditional C++ approach for storing OR-combinations of enum values is to
 // use an int or unsigned int variable. The inconvenience with this approach is
 // that there's no type checking at all; any enum value can be OR'd with any
 // other enum value and passed on to a function that takes an int or unsigned
 // int.
 template <typename T, typename S = int>
 class Flags FINAL {
  public:
   typedef T flag_type;
   typedef S mask_type;
 
   Flags() : mask_(0) {}
-  Flags(flag_type flag) : mask_(flag) {}  // NOLINT(runtime/explicit)
-  explicit Flags(mask_type mask) : mask_(mask) {}
+  Flags(flag_type flag)  // NOLINT(runtime/explicit)
+      : mask_(static_cast<S>(flag)) {}
+  explicit Flags(mask_type mask) : mask_(static_cast<S>(mask)) {}
 
   Flags& operator&=(const Flags& flags) {
     mask_ &= flags.mask_;
     return *this;
   }
   Flags& operator|=(const Flags& flags) {
     mask_ |= flags.mask_;
     return *this;
   }
   Flags& operator^=(const Flags& flags) {
@@ skipping 60 matching lines @@
   inline Type operator^(Type::flag_type lhs, const Type& rhs) {               \
     return rhs ^ lhs;                                                         \
   } inline void operator^(Type::flag_type lhs, Type::mask_type rhs)           \
       ALLOW_UNUSED_TYPE;                                                      \
   inline void operator^(Type::flag_type lhs, Type::mask_type rhs) {}
 
 }  // namespace base
 }  // namespace v8
 
 #endif  // V8_BASE_FLAGS_H_