Use the std::chrono to get the time.

[ Merge of http://go/wvgerrit/67985 ]

Now that we can use C++11, we should use the cross-platform types for
clocks instead of the platform-specific versions.

Test: WV unit/integration tests.
Change-Id: I50318e3d1caf9e814f33f497f83c19c9f3c154a1

libwvdrmengine/cdm/metrics/include/timer_metric.h

@@ -1,7 +1,7 @@
 #ifndef WVCDM_METRICS_TIMER_METRIC_H_
 #define WVCDM_METRICS_TIMER_METRIC_H_
 
-#include <stdint.h>
+#include <chrono>
 
 namespace wvcdm {
 namespace metrics {
@@ -23,8 +23,8 @@ class TimerMetric {
   double AsUs() const;
 
  private:
-  double sec_;
-  double usec_;
+  std::chrono::steady_clock clock_;
+  std::chrono::time_point<std::chrono::steady_clock> start_;
   bool is_started_;
 
 };

libwvdrmengine/cdm/metrics/src/timer_metric.cpp

@@ -1,39 +1,23 @@
 #include "timer_metric.h"
 
-#include <stddef.h>
-#include <sys/time.h>
-
 namespace wvcdm {
 namespace metrics {
 
 void TimerMetric::Start() {
-  struct timeval tv;
-  gettimeofday(&tv, NULL);
-  sec_ = tv.tv_sec;
-  usec_ = tv.tv_usec;
+  start_ = clock_.now();
   is_started_ = true;
 }
 
 void TimerMetric::Clear() {
   is_started_ = false;
-  sec_ = 0;
-  usec_ = 0;
 }
 
 double TimerMetric::AsMs() const {
-  struct timeval tv;
-  gettimeofday(&tv, NULL);
-  return usec_ > tv.tv_usec ?
-      (tv.tv_sec - sec_ - 1) * 1000.0 + (tv.tv_usec - usec_ + 1000000.0) / 1000.0 :
-      (tv.tv_sec - sec_) * 1000.0 + (tv.tv_usec - usec_) / 1000.0;
+ return (clock_.now() - start_) / std::chrono::milliseconds(1);
 }
 
 double TimerMetric::AsUs() const {
-  struct timeval tv;
-  gettimeofday(&tv, NULL);
-  return usec_ > tv.tv_usec ?
-      (tv.tv_sec - sec_ - 1) * 1000000.0 + (tv.tv_usec - usec_ + 1000000.0) :
-      (tv.tv_sec - sec_) * 1000000.0 + (tv.tv_usec - usec_);
+ return (clock_.now() - start_) / std::chrono::microseconds(1);
 }
 
 }  // namespace metrics