Clean up some Mac memory code.

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 45 matching lines @@
 // priv:           Pages mapped only by this process.
 // shared:         PSS or 0 if the kernel doesn't support this.
 // shareable:      0
 
 // On ChromeOS:
 // priv:           Pages mapped only by this process.
 // shared:         PSS or 0 if the kernel doesn't support this.
 // shareable:      0
 // swapped         Pages swapped out to zram.
 //
-// On OS X: TODO(thakis): Revise.
-// priv:           Memory.
+// On macOS:
+// priv:           Resident size (RSS) including shared memory. Warning: This
+//                 does not include compressed size and does not always
+//                 accurately account for shared memory due to things like
+//                 copy-on-write. TODO(erikchen): Revamp this with something
+//                 more accurate.
 // shared:         0
 // shareable:      0
 //
 struct WorkingSetKBytes {
   WorkingSetKBytes() : priv(0), shareable(0), shared(0) {}
   size_t priv;
   size_t shareable;
   size_t shared;
 #if defined(OS_CHROMEOS)
   size_t swapped;
@@ skipping 381 matching lines @@
   SystemDiskInfo disk_info_;
 #endif
 #if defined(OS_CHROMEOS)
   SwapInfo swap_info_;
 #endif
 };
 
 }  // namespace base
 
 #endif  // BASE_PROCESS_PROCESS_METRICS_H_