Make UMA_HISTOGRAM_ENUMERATION work with scoped enums.

base/metrics/histogram_macros_unittest.cc

 // Copyright 2015 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.
 
 #include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 TEST(ScopedHistogramTimer, TwoTimersOneScope) {
   SCOPED_UMA_HISTOGRAM_TIMER("TestTimer0");
   SCOPED_UMA_HISTOGRAM_TIMER("TestTimer1");
   SCOPED_UMA_HISTOGRAM_LONG_TIMER("TestLongTimer0");
   SCOPED_UMA_HISTOGRAM_LONG_TIMER("TestLongTimer1");
 }
 
+// Compile tests for UMA_HISTOGRAM_ENUMERATION with the three different types it
+// accepts:
+// - integral types
+// - unscoped enums
+// - scoped enums
+TEST(HistogramMacro, IntegralPsuedoEnumeration) {
+  UMA_HISTOGRAM_ENUMERATION("Test.FauxEnumeration", 1, 10000);
+}
+
+TEST(HistogramMacro, UnscopedEnumeration) {
+  enum TestEnum : char {
+    FIRST_VALUE,
+    SECOND_VALUE,
+    THIRD_VALUE,
+    MAX_ENTRIES,
+  };
+  UMA_HISTOGRAM_ENUMERATION("Test.UnscopedEnumeration", SECOND_VALUE,
+                            MAX_ENTRIES);
+}
+
+TEST(HistogramMacro, ScopedEnumeration) {
+  enum class TestEnum {
+    FIRST_VALUE,
+    SECOND_VALUE,
+    THIRD_VALUE,
+    MAX_ENTRIES,
+  };
+  UMA_HISTOGRAM_ENUMERATION("Test.ScopedEnumeration", TestEnum::SECOND_VALUE,
+                            TestEnum::MAX_ENTRIES);
+}
+
 }  // namespace base