Fix a potential multi-thread issue when manipulating removable storage map

base/system_monitor/system_monitor.h

 // Copyright (c) 2012 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.
 
 #ifndef BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_
 #define BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_
 
 #include <map>
 #include <string>
 #include <vector>
 

[vandebo (ex-Chrome), 2012/09/12 17:12:57]

Should include the lock header.

 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/string16.h"
 #include "build/build_config.h"
 
 // Windows HiRes timers drain the battery faster so we need to know the battery
 // status.  This isn't true for other platforms.
 #if defined(OS_WIN)
 #define ENABLE_BATTERY_MONITORING 1
@@ skipping 66 matching lines @@
   // This function must be called before instantiating an instance of the class
   // and before the Sandbox is initialized.
 #if !defined(OS_IOS)
   static void AllocateSystemIOPorts();
 #else
   static void AllocateSystemIOPorts() {}
 #endif  // OS_IOS
 #endif  // OS_MACOSX
 
   // Returns information for attached removable storage.
-  std::vector<RemovableStorageInfo> GetAttachedRemovableStorage() const;
+  std::vector<RemovableStorageInfo> GetAttachedRemovableStorage();

[willchan no longer on Chromium, 2012/09/12 17:00:45]

This should probably stay const. If you only need the const for the Lock, then
make the Lock mutable.

[vandebo (ex-Chrome), 2012/09/12 17:12:57]

Hmm, I haven't seen a lot of mutable annotations in Chrome.  codesearch shows
that it's mostly used for locks.  Thanks.

Unchecked the commit box since I noticed a couple more minor things too.

 
   //
   // Power-related APIs
   //
 
   // Is the computer currently on battery power.
   // Can be called on any thread.
   bool BatteryPower() const {
     // Using a lock here is not necessary for just a bool.
     return battery_in_use_;
@@ skipping 103 matching lines @@
 
 #if defined(ENABLE_BATTERY_MONITORING)
   base::OneShotTimer<SystemMonitor> delayed_battery_check_;
 #endif
 
 #if defined(OS_IOS)
   // Holds pointers to system event notification observers.
   std::vector<id> notification_observers_;
 #endif
 
+  // The lock for manipluating removable_storage_map_ structure.

[vandebo (ex-Chrome), 2012/09/12 17:12:57]

nit: Remove the: "Lock for..."

+  base::Lock removable_storage_lock_;
   // Map of all the attached removable storage devices.
   RemovableStorageMap removable_storage_map_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemMonitor);
 };
 
 }  // namespace base
 
 #endif  // BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_