Use TimeTicks instead of gettimeofday in ProcessMetrics.

base/process/process_metrics_linux.cc

Index: base/process/process_metrics_linux.cc
diff --git a/base/process/process_metrics_linux.cc b/base/process/process_metrics_linux.cc
index 7fa50922d572575206532ce1fee30d9235a58b72..0e12595f92efd10a76bf477bcebcd533257d385d 100644
--- a/base/process/process_metrics_linux.cc
+++ b/base/process/process_metrics_linux.cc
@@ -182,20 +182,16 @@ bool ProcessMetrics::GetWorkingSetKBytes(WorkingSetKBytes* ws_usage) const {
 }
 
 double ProcessMetrics::GetCPUUsage() {
-  struct timeval now;
-  int retval = gettimeofday(&now, NULL);
-  if (retval)
-    return 0;
-  int64 time = TimeValToMicroseconds(now);
+  TimeTicks time = TimeTicks::Now();
 
-  if (last_cpu_time_ == 0) {
+  if (last_cpu_ == 0) {
     // First call, just set the last values.
     last_cpu_time_ = time;
     last_cpu_ = GetProcessCPU(process_);
     return 0;
   }
 
-  int64 time_delta = time - last_cpu_time_;
+  int64 time_delta = (time - last_cpu_time_).InMicroseconds();
   DCHECK_NE(time_delta, 0);
   if (time_delta == 0)
     return 0;
@@ -263,7 +259,6 @@ bool ProcessMetrics::GetIOCounters(IoCounters* io_counters) const {
 
 ProcessMetrics::ProcessMetrics(ProcessHandle process)
     : process_(process),
-      last_cpu_time_(0),
       last_system_time_(0),
       last_cpu_(0) {
   processor_count_ = base::SysInfo::NumberOfProcessors();