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..29937d8bced3818f78f57fb09f8774e446437a94 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 +122,43 @@ void SystemMonitor::ProcessRemovableStorageDetached(const std::string& id) {
   NotifyRemovableStorageDetached(id);
 }
 
+void SystemMonitor::ProcessStorageFreeSpaceChanged(
+    const FilePath::StringType& path) {
+  DVLOG(1) << "Free Space Changing";
+  devices_changed_observer_list_->Notify(
+      &DevicesChangedObserver::OnStorageFreeSpaceChanged, path);
+}
+
+bool SystemMonitor::StartWatchingStorage(const FilePath::StringType& path) {
+  if (!free_space_delegate_)
+    return false;
+
+  // Try to start watching if the first one is requested.
+  if (watched_storages_.find(path) == watched_storages_.end() &&
+      !free_space_delegate_->StartWatchingStorage(path)) {
+    return false;
+  }
+
+  // The free space watcher has been started for the storage identifed by
+  // |path|.
+  watched_storages_.insert(path);
+  return true;
+}
+
+bool SystemMonitor::StopWatchingStorage(const FilePath::StringType& path) {
+  if (!free_space_delegate_)
+    return false;
+
+  watched_storages_.erase(path);
+
+  // Try to stop watching when the last one is erased.
+  if (watched_storages_.find(path) == watched_storages_.end() &&
+      !free_space_delegate_->StopWatchingStorage(path))
+    return false;
+
+  return true;
+}
+
 std::vector<SystemMonitor::RemovableStorageInfo>
 SystemMonitor::GetAttachedRemovableStorage() const {
   std::vector<RemovableStorageInfo> results;