Re-enable the clang check for enum constants.

tools/clang/plugins/tests/enum_last_value.cpp

+// 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.
+
+// We warn when xxxLAST constants aren't last.
+enum BadOne {
+  kBadOneInvalid = -1,
+  kBadOneRed,
+  kBadOneGreen,
+  kBadOneBlue,
+  kBadOneLast = kBadOneGreen
+};
+
+// We warn when xxx_LAST constants aren't last.
+enum BadTwo {
+  BAD_TWO_INVALID,
+  BAD_TWO_RED,
+  BAD_TWO_GREEN,
+  BAD_TWO_BLUE = 0xfffffffc,
+  BAD_TWO_LAST = BAD_TWO_GREEN
+};
+
+// We dont warn when xxxLAST constants are last.
+enum GoodOne {
+  kGoodOneInvalid = -1,
+  kGoodOneRed,
+  kGoodOneGreen,
+  kGoodOneBlue,
+  kGoodOneLast = kGoodOneBlue
+};
+
+// We dont warn when xxx_LAST constants are last.
+enum GoodTwo {
+  GOOD_TWO_INVALID,
+  GOOD_TWO_RED,
+  GOOD_TWO_GREEN,
+  GOOD_TWO_BLUE = 0xfffffffc,
+  GOOD_TWO_LAST = GOOD_TWO_BLUE
+};