Make task manager memory data more efficient and meaningful.

base/process/process_metrics.h

Index: base/process/process_metrics.h
diff --git a/base/process/process_metrics.h b/base/process/process_metrics.h
index 5916b94148cb2e6e9a6782096bcca49fd7b8f41a..8b4ec86693ac9aaceae50b1ce77d8549eaf32565 100644
--- a/base/process/process_metrics.h
+++ b/base/process/process_metrics.h
@@ -140,7 +140,8 @@ class BASE_EXPORT ProcessMetrics {
   // memory usage as per definition of CommittedBytes.
   void GetCommittedKBytes(CommittedKBytes* usage) const;
   // Fills a WorkingSetKBytes containing resident private and shared memory
-  // usage in bytes, as per definition of WorkingSetBytes.
+  // usage in bytes, as per definition of WorkingSetBytes. Note that this
+  // function is somewhat expensive on Windows (a few ms per process).
   bool GetWorkingSetKBytes(WorkingSetKBytes* ws_usage) const;
 
 #if defined(OS_MACOSX)