[NOT TO COMMIT YET] Using proc/pid/status file contents to get process metrics in linux.

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 54b10aaacfa2f5cfb0ab3ffc702fbc226435c325..f637a05f4f0fdf5ce58e8c189322d7cbba7093ce 100644
--- a/base/process/process_metrics.h
+++ b/base/process/process_metrics.h
@@ -144,6 +144,13 @@ class BASE_EXPORT ProcessMetrics {
   // function is somewhat expensive on Windows (a few ms per process).
   bool GetWorkingSetKBytes(WorkingSetKBytes* ws_usage) const;
 
+#if defined(OS_LINUX) || defined(OS_ANDROID)
+  // Returns the current and the peak resident set size on passing a file
+  // descriptor to "proc/<pid>/status" file:
+  size_t GetWorkingSetSize(int proc_status_fd) const;
+  size_t GetPeakWorkingSetSize(int proc_status_fd) const;
+#endif
+
 #if defined(OS_MACOSX)
   // Fills both CommitedKBytes and WorkingSetKBytes in a single operation. This
   // is more efficient on Mac OS X, as the two can be retrieved with a single