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

chrome/browser/storage_monitor/storage_monitor.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/storage_monitor/storage_monitor.h"
 
 #include "base/stl_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/storage_monitor/removable_storage_observer.h"
 #include "chrome/browser/storage_monitor/transient_device_ids.h"
@@ skipping 43 matching lines @@
 
   base::AutoLock lock(storage_lock_);
   for (RemovableStorageMap::const_iterator it = storage_map_.begin();
        it != storage_map_.end();
        ++it) {
     results.push_back(it->second);
   }
   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();
     return;
   }
 
   if (!callback.is_null()) {
     on_initialize_callbacks_.push_back(callback);
   }
-
-  Init();
 }
 
 bool StorageMonitor::IsInitialized() {
   return initialized_;
 }
 
 void StorageMonitor::AddObserver(RemovableStorageObserver* obs) {
   observer_list_->AddObserver(obs);
 }
 
@@ skipping 80 matching lines @@
     info = it->second;
     storage_map_.erase(it);
   }
 
   DVLOG(1) << "RemovableStorageDetached for id " << id;
   observer_list_->Notify(
       &RemovableStorageObserver::OnRemovableStorageDetached, info);
 }
 
 }  // namespace chrome