Add, test, and use clock utilities

util/misc/clock_mac.cc

Index: util/misc/clock_mac.cc
diff --git a/util/misc/clock_mac.cc b/util/misc/clock_mac.cc
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index 0000000000000000000000000000000000000000..bb52299efa9e172c6847e60aaf303f6899f78d4c
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+++ b/util/misc/clock_mac.cc
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+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "util/misc/clock.h"
+
+#include <mach/mach_time.h>
+
+#include "base/mac/mach_logging.h"
+
+namespace {
+
+mach_timebase_info_data_t* TimebaseInternal() {
+  mach_timebase_info_data_t* timebase_info = new mach_timebase_info_data_t;
+  kern_return_t kr = mach_timebase_info(timebase_info);
+  MACH_CHECK(kr == KERN_SUCCESS, kr) << "mach_timebase_info";
+  return timebase_info;
+}
+
+mach_timebase_info_data_t* Timebase() {
+  static mach_timebase_info_data_t* timebase_info = TimebaseInternal();
+  return timebase_info;
+}
+
+}  // namespace
+
+namespace crashpad {
+
+uint64_t ClockMonotonicNanoseconds() {
+  uint64_t absolute_time = mach_absolute_time();
+  mach_timebase_info_data_t* timebase_info = Timebase();
+  return absolute_time * timebase_info->numer / timebase_info->denom;
+}
+
+}  // namespace crashpad