Revert of SkTime::GetNSecs()

tools/timer/SysTimer_mach.cpp

+/*
+ * Copyright 2011 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "SysTimer_mach.h"
+
+static time_value_t mac_cpu_time() {
+    mach_port_t task = mach_task_self();
+    if (task == MACH_PORT_NULL) {
+        time_value_t none = {0, 0};
+        return none;
+    }
+
+    task_thread_times_info thread_info_data;
+    mach_msg_type_number_t thread_info_count = TASK_THREAD_TIMES_INFO_COUNT;
+    if (KERN_SUCCESS != task_info(task,
+                                  TASK_THREAD_TIMES_INFO,
+                                  reinterpret_cast<task_info_t>(&thread_info_data),
+                                  &thread_info_count)) {
+        time_value_t none = {0, 0};
+        return none;
+    }
+
+    time_value_add(&thread_info_data.user_time, &thread_info_data.system_time)
+    return thread_info_data.user_time;
+}
+
+static double interval_in_ms(time_value_t start_clock, time_value_t end_clock) {
+    double duration_clock;
+    if ((end_clock.microseconds - start_clock.microseconds) < 0) {
+        duration_clock = (end_clock.seconds - start_clock.seconds-1) * 1000;
+        duration_clock += (1000000 + end_clock.microseconds - start_clock.microseconds) / 1000.0;
+    } else {
+        duration_clock = (end_clock.seconds - start_clock.seconds) * 1000;
+        duration_clock += (end_clock.microseconds - start_clock.microseconds) / 1000.0;
+    }
+    return duration_clock;
+}
+
+void SysTimer::startWall() {
+    fStartWall = mach_absolute_time();
+}
+
+void SysTimer::startCpu() {
+    fStartCpu = mac_cpu_time();
+}
+
+double SysTimer::endCpu() {
+    time_value_t end_cpu = mac_cpu_time();
+    return interval_in_ms(fStartCpu, end_cpu);
+}
+
+double SysTimer::endWall() {
+    uint64_t end_wall = mach_absolute_time();
+
+    uint64_t elapsed = end_wall - fStartWall;
+    mach_timebase_info_data_t sTimebaseInfo;
+    if (KERN_SUCCESS != mach_timebase_info(&sTimebaseInfo)) {
+        return 0;
+    } else {
+        uint64_t elapsedNano = elapsed * sTimebaseInfo.numer / sTimebaseInfo.denom;
+        return elapsedNano / 1000000.0;
+    }
+}