Isolated FS for media devices.

base/system_monitor/system_monitor.cc

Index: base/system_monitor/system_monitor.cc
diff --git a/base/system_monitor/system_monitor.cc b/base/system_monitor/system_monitor.cc
index 22f91d777108649c90c97915ce471b724c243304..d1dd4391cc4a2b68871b4dd77ab0fc4f15e9d529 100644
--- a/base/system_monitor/system_monitor.cc
+++ b/base/system_monitor/system_monitor.cc
@@ -104,8 +104,9 @@ void SystemMonitor::ProcessMediaDeviceAttached(
 
 void SystemMonitor::ProcessMediaDeviceDetached(const std::string& id) {
   MediaDeviceMap::iterator it = media_device_map_.find(id);
-  if (it != media_device_map_.end())
-    media_device_map_.erase(it);
+  if (it == media_device_map_.end())
+    return;
+  media_device_map_.erase(it);
   NotifyMediaDeviceDetached(id);
 }