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

base/system_monitor/system_monitor.h

Index: base/system_monitor/system_monitor.h
diff --git a/base/system_monitor/system_monitor.h b/base/system_monitor/system_monitor.h
index 48d512b708c11aa44368c05300dd9a38f29e00ed..45e8a75dcaf7fc79361034c5614f8052ca7390de 100644
--- a/base/system_monitor/system_monitor.h
+++ b/base/system_monitor/system_monitor.h
@@ -95,7 +95,7 @@ class BASE_EXPORT SystemMonitor {
 #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
@@ -219,6 +219,8 @@ class BASE_EXPORT SystemMonitor {
   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_;