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 f6ab819f5fc405f9788a75ad186172beec404e67..78a39c63eb6e4e705dba197161171614d30bfb02 100644
--- a/base/process/process_metrics_linux.cc
+++ b/base/process/process_metrics_linux.cc
@@ -181,20 +181,16 @@ 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_walltime_ = time;
     last_cpu_ = GetProcessCPU(process_);
     return 0;
   }
 
-  int64 time_delta = time - last_cpu_time_;
+  int64 time_delta = (time - last_cpu_walltime_).InMicroseconds();
   DCHECK_NE(time_delta, 0);
   if (time_delta == 0)
     return 0;
@@ -209,7 +205,7 @@ double ProcessMetrics::GetCPUUsage() {
   int percentage = 100 * (cpu_time - last_cpu_time).InSecondsF() /
       TimeDelta::FromMicroseconds(time_delta).InSecondsF();
 
-  last_cpu_time_ = time;
+  last_cpu_walltime_ = time;
   last_cpu_ = cpu;
 
   return percentage;
@@ -262,7 +258,6 @@ 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();