Cleanup bits of base::ProcessMetrics.

Review URL: https://codereview.chromium.org/549753002

Cr-Commit-Position: refs/heads/master@{#293791}

base/process/process_metrics.cc

@@ -53,7 +53,7 @@ double ProcessMetrics::GetPlatformIndependentCPUUsage() {
 
 #if !defined(OS_MACOSX)
 int ProcessMetrics::GetIdleWakeupsPerSecond() {
-  NOTIMPLEMENTED();  // http://crbug.com/20488
+  NOTIMPLEMENTED();  // http://crbug.com/120488
   return 0;
 }
 #endif  // !defined(OS_MACOSX)

base/process/process_metrics.h

@@ -202,9 +202,11 @@ class BASE_EXPORT ProcessMetrics {
   TimeTicks last_cpu_time_;
   int64 last_system_time_;
 
+#if defined(OS_MACOSX)
   // Same thing for idle wakeups.
   TimeTicks last_idle_wakeups_time_;
-  int64 last_absolute_idle_wakeups_;
+  uint64 last_absolute_idle_wakeups_;
+#endif
 
 #if !defined(OS_IOS)
 #if defined(OS_MACOSX)
@@ -320,7 +322,7 @@ struct BASE_EXPORT SystemDiskInfo {
   uint64 weighted_io_time;
 };
 
-// Checks whether the candidate string is a valid disk name, [sh]d[a-z]+
+// Checks whether the candidate string is a valid disk name, [hsv]d[a-z]+
 // for a generic disk or mmcblk[0-9]+ for the MMC case.
 // Names of disk partitions (e.g. sda1) are not valid.
 BASE_EXPORT bool IsValidDiskName(const std::string& candidate);

base/process/process_metrics_mac.cc

@@ -312,9 +312,10 @@ int ProcessMetrics::GetIdleWakeupsPerSecond() {
 
   int64 wakeups_delta = absolute_idle_wakeups - last_absolute_idle_wakeups_;
   int64 time_delta = (time - last_idle_wakeups_time_).InMicroseconds();
-  DCHECK_NE(0U, time_delta);
-  if (time_delta == 0)
+  if (time_delta == 0) {
+    NOTREACHED();
     return 0;
+  }
 
   last_idle_wakeups_time_ = time;
   last_absolute_idle_wakeups_ = absolute_idle_wakeups;