[SystemInfo API] Implement storage.getAvailableCapacity API

chrome/browser/extensions/api/system_storage/system_storage_api.h

 // Copyright 2013 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_SYSTEM_STORAGE_SYSTEM_STORAGE_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_SYSTEM_STORAGE_SYSTEM_STORAGE_API_H_
 
 #include "chrome/browser/extensions/api/system_storage/storage_info_provider.h"
 #include "chrome/browser/extensions/extension_function.h"
 #include "chrome/browser/storage_monitor/storage_monitor.h"
@@ skipping 26 matching lines @@
   // AsyncExtensionFunction overrides.
   virtual bool RunImpl() OVERRIDE;
 
  private:
   void OnStorageMonitorInit(const std::string& transient_device_id);
 
   // Eject device request handler.
   void HandleResponse(StorageMonitor::EjectStatus status);
 };
 
+class SystemStorageGetAvailableCapacityFunction
+    : public AsyncExtensionFunction {
+ public:
+  DECLARE_EXTENSION_FUNCTION("system.storage.getAvailableCapacity",
+                             SYSTEM_STORAGE_GETAVAILABLECAPACITY);
+  SystemStorageGetAvailableCapacityFunction();
+
+ private:
+  void OnStorageMonitorInit(const std::string& transient_id);
+  void OnQueryCompleted(const std::string& transient_id,
+                        double available_capacity);
+  virtual ~SystemStorageGetAvailableCapacityFunction();
+  virtual bool RunImpl() OVERRIDE;
+};
+
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SYSTEM_STORAGE_SYSTEM_STORAGE_API_H_