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

base/process/process_metrics.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains routines for gathering resource statistics for processes
 // running on the system.
 
 #ifndef BASE_PROCESS_PROCESS_METRICS_H_
 #define BASE_PROCESS_PROCESS_METRICS_H_
 
@@ skipping 126 matching lines @@
   bool GetMemoryBytes(size_t* private_bytes,
                       size_t* shared_bytes);
   // Fills a CommittedKBytes with both resident and paged
   // 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. Note that this
   // 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
   // system call.
   bool GetCommittedAndWorkingSetKBytes(CommittedKBytes* usage,
                                        WorkingSetKBytes* ws_usage) const;
 #endif
 
   // Returns the CPU usage in percent since the last time this method or
   // GetPlatformIndependentCPUUsage() was called. The first time this method
@@ skipping 246 matching lines @@
   SystemDiskInfo disk_info_;
 #endif
 #if defined(OS_CHROMEOS)
   SwapInfo swap_info_;
 #endif
 };
 
 }  // namespace base
 
 #endif  // BASE_PROCESS_PROCESS_METRICS_H_