[SystemInfo API] Rewrite storage info provider using storage monitor impl

chrome/browser/storage_monitor/storage_monitor.cc

Index: chrome/browser/storage_monitor/storage_monitor.cc
diff --git a/chrome/browser/storage_monitor/storage_monitor.cc b/chrome/browser/storage_monitor/storage_monitor.cc
index 682264223c40b147f4446a65e51ef9b9b042da53..c781feb7e651e2689b6d71415774ece128f25426 100644
--- a/chrome/browser/storage_monitor/storage_monitor.cc
+++ b/chrome/browser/storage_monitor/storage_monitor.cc
@@ -61,7 +61,18 @@ std::vector<StorageInfo> StorageMonitor::GetAttachedStorage() const {
   return results;
 }
 
+std::vector<StorageInfo> StorageMonitor::GetAllAvailableStorages() const {
+  // Returns empty vector as default implemenation.
+  return std::vector<StorageInfo>();
+}
+
 void StorageMonitor::Initialize(base::Closure callback) {
+  RegisterInitCompletedCallback(callback);
+  Init();
+}
+
+void StorageMonitor::RegisterInitCompletedCallback(
+    base::Closure callback) {
   if (initialized_) {
     if (!callback.is_null())
       callback.Run();
@@ -71,8 +82,6 @@ void StorageMonitor::Initialize(base::Closure callback) {
   if (!callback.is_null()) {
     on_initialize_callbacks_.push_back(callback);
   }
-
-  Init();
 }
 
 bool StorageMonitor::IsInitialized() {