Extend the capability of SystemMonitor to support watching storage free space change

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 f30c8935c9a999b38382f78e879c9319a4eba13f..c48b44eac9359a59f69f4cb871a7f93660e5b75f 100644
--- a/base/system_monitor/system_monitor.cc
+++ b/base/system_monitor/system_monitor.cc
@@ -39,7 +39,8 @@ SystemMonitor::SystemMonitor()
       devices_changed_observer_list_(
           new ObserverListThreadSafe<DevicesChangedObserver>()),
       battery_in_use_(false),
-      suspended_(false) {
+      suspended_(false),
+      free_space_delegate_(NULL) {
   DCHECK(!g_system_monitor);
   g_system_monitor = this;
 
@@ -121,6 +122,17 @@ void SystemMonitor::ProcessRemovableStorageDetached(const std::string& id) {
   NotifyRemovableStorageDetached(id);
 }
 
+void SystemMonitor::ProcessStorageFreeSpaceChanged(const FilePath& path,
+                                                   int64 available_capacity) {
+  DVLOG(1) << "Free Space Changing: " << path.value() << " "
+           << available_capacity << " bytes";
+  if (ContainsKey(free_space_changed_observer_map_, path) &&

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

This needs to be locked.

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

Use find so you only look up the path once.  (elsewhere too)

[Hongbo Min, 2012/09/13 13:40:53]

Done.

[Hongbo Min, 2012/09/13 13:40:53]

Done.

+      free_space_changed_observer_map_[path].get())
+    free_space_changed_observer_map_[path]->Notify(
+        &StorageFreeSpaceChangedObserver::OnStorageFreeSpaceChanged,
+        path, available_capacity);
+}
+
 std::vector<SystemMonitor::RemovableStorageInfo>
 SystemMonitor::GetAttachedRemovableStorage() const {
   std::vector<RemovableStorageInfo> results;
@@ -148,6 +160,42 @@ void SystemMonitor::RemoveDevicesChangedObserver(DevicesChangedObserver* obs) {
   devices_changed_observer_list_->RemoveObserver(obs);
 }
 
+void SystemMonitor::AddStorageFreeSpaceChangedObserver(
+    const FilePath& path,
+    StorageFreeSpaceChangedObserver* obs) {
+  {
+    base::AutoLock lock(free_space_observers_lock_);
+    if (!ContainsKey(free_space_changed_observer_map_, path))
+      free_space_changed_observer_map_[path] =
+        new StorageFreeSpaceChangedObserverList();

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

nit: Omit () when using new with a constructor that has zero arguments.

[Hongbo Min, 2012/09/13 13:40:53]

Done.

+
+    watching_storage_set_.insert(path);
+    free_space_changed_observer_map_[path]->AddObserver(obs);
+  }
+
+  if (!free_space_delegate_->IsWatchingStorage(path))
+    free_space_delegate_->StartWatchingStorage(path);

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

Hmm, consumers can call AddStorageFreeSpaceChangedObserver from any thread.  We
should probably record the thread that the delegate was set on and then post a
task to that thread whenever we invoke a method of the delegate.  We should also
document that behavior in a comment in the delegate definition.

[Hongbo Min, 2012/09/13 13:40:53]

Done. See the code comment of StorageFreeSpaceDelegate definition.

+}
+
+void SystemMonitor::RemoveStorageFreeSpaceChangedObserver(
+    const FilePath& path,
+  StorageFreeSpaceChangedObserver* obs) {
+  base::AutoLock lock(free_space_observers_lock_);
+
+  std::multiset<FilePath>::iterator it = watching_storage_set_.find(path);
+  // Nobody is interested in the given |path|.
+  if (it == watching_storage_set_.end())
+    return;
+
+  free_space_changed_observer_map_[path]->RemoveObserver(obs);
+  watching_storage_set_.erase(it);
+
+  // Try to stop watching the storage if the last observer is removed.
+  if (!ContainsKey(watching_storage_set_, path) &&
+      free_space_delegate_->IsWatchingStorage(path))
+    free_space_delegate_->StopWatchingStorage(path);
+}
+
 void SystemMonitor::NotifyDevicesChanged(DeviceType device_type) {
   DVLOG(1) << "DevicesChanged with device type " << device_type;
   devices_changed_observer_list_->Notify(