Revert of SkTime::GetNSecs()

tools/timer/SysTimer_posix.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_posix.h"
+
+static double interval_in_ms(timespec start_clock, timespec end_clock)
+{
+    double duration_clock;
+    if ((end_clock.tv_nsec - start_clock.tv_nsec) < 0) {
+        duration_clock = (end_clock.tv_sec - start_clock.tv_sec - 1) * 1000;
+        duration_clock += (1000000000 + end_clock.tv_nsec - start_clock.tv_nsec) / 1000000.0;
+    } else {
+        duration_clock = (end_clock.tv_sec - start_clock.tv_sec) * 1000;
+        duration_clock += (end_clock.tv_nsec - start_clock.tv_nsec) / 1000000.0;
+    }
+    return duration_clock;
+}
+
+void SysTimer::startWall() {
+    if (-1 == clock_gettime(CLOCK_MONOTONIC, &fWall)) {
+        timespec none = {0, 0};
+        fWall = none;
+    }
+}
+void SysTimer::startCpu() {
+    if (-1 == clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &fCpu)) {
+        timespec none = {0, 0};
+        fCpu = none;
+    }
+}
+
+double SysTimer::endCpu() {
+    timespec end_cpu;
+    if (-1 == clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end_cpu)) {
+        timespec none = {0, 0};
+        end_cpu = none;
+    }
+    return interval_in_ms(fCpu, end_cpu);
+}
+
+double SysTimer::endWall() {
+    timespec end_wall;
+    if (-1 == clock_gettime(CLOCK_MONOTONIC, &end_wall)) {
+        timespec none = {0, 0};
+        end_wall = none;
+    }
+    return interval_in_ms(fWall, end_wall);
+}