[SystemInfo API] Implement systemInfo.storage.onAvailableCapacityChanged event

chrome/browser/extensions/api/system_info_storage/storage_info_observer.h

Index: chrome/browser/extensions/api/system_info_storage/storage_info_observer.h
diff --git a/chrome/browser/extensions/api/system_info_storage/storage_info_observer.h b/chrome/browser/extensions/api/system_info_storage/storage_info_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..023404a08cfa3925f11d55ce289804067912161f
--- /dev/null
+++ b/chrome/browser/extensions/api/system_info_storage/storage_info_observer.h
@@ -0,0 +1,22 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.

[benwells, 2013/01/31 04:04:57]

Nit: the (c) should be removed, and 2012->2013.

[Hongbo Min, 2013/02/01 07:06:50]

Done.

[benwells, 2013/02/04 04:21:41]

Still-a-nit: the (c) should be removed for new copyright headers

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#ifndef CHROME_BROWSER_EXTENSIONS_STORAGE_INFO_OBSERVER_H_
+#define CHROME_BROWSER_EXTENSIONS_STORAGE_INFO_OBSERVER_H_
+
+namespace extensions {
+
+// Observes the free space changes happening on the storage.
+class StorageInfoObserver {
+ public:
+  virtual ~StorageInfoObserver() {}
+
+  // Called when the storage free space changes.
+  virtual void OnStorageFreeSpaceChanged(const std::string& id,
+                                         double old_value,
+                                         double new_value) = 0;
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_STORAGE_INFO_OBSERVER_H_