cc: Add DEFINE_ENUM macro.

cc/base/util.h

 // Copyright 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 CC_BASE_UTIL_H_
 #define CC_BASE_UTIL_H_
 
 #include <limits>
 
 #include "base/basictypes.h"
 
+// Declares an enum for which the values can be used to index an array.
+// In addition to the enum, this also declares 3 constants. enumname_MIN,
+// enumname_MAX and enumname_ARRAYSIZE. The last can be used to declare
+// an array that is large enough to allow indexing using all enum values.
+#define DEFINE_ENUM(name, ...)                                       \
+    enum name { __VA_ARGS__ };                                       \
+    const name name ## _MIN = static_cast<name>(0);                  \
+    const name name ## _MAX = static_cast<name>(                     \
+        sizeof((int[]) { __VA_ARGS__ }) / sizeof(name ## _MIN) - 1); \
+    const int name ## _ARRAYSIZE = name ## _MAX + 1
+
 namespace cc {
 
 template <typename T> T RoundUp(T n, T mul) {
   COMPILE_ASSERT(std::numeric_limits<T>::is_integer, type_must_be_integral);
   return (n > 0) ? ((n + mul - 1) / mul) * mul
                  : (n / mul) * mul;
 }
 
 template <typename T> T RoundDown(T n, T mul) {
   COMPILE_ASSERT(std::numeric_limits<T>::is_integer, type_must_be_integral);
   return (n > 0) ? (n / mul) * mul
                  : (n == 0) ? 0
                  : ((n - mul + 1) / mul) * mul;
 }
 
 }  // namespace cc
 
 #endif  // CC_BASE_UTIL_H_