[SystemInfo API] Implement systemInfo.storage.onAvailableCapacityChanged event

chrome/browser/extensions/system_info_provider.h

 // 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.
 #ifndef CHROME_BROWSER_EXTENSIONS_SYSTEM_INFO_PROVIDER_H_
 #define CHROME_BROWSER_EXTENSIONS_SYSTEM_INFO_PROVIDER_H_
 
 #include <queue>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 58 matching lines @@
 
     is_waiting_for_completion_ = true;
 
     base::SequencedWorkerPool* worker_pool =
         content::BrowserThread::GetBlockingPool();
     // The query task posted to the worker pool won't block shutdown, and any
     // running query task at shutdown time will be ignored.
     worker_pool->PostSequencedWorkerTaskWithShutdownBehavior(
           worker_pool_token_,
           FROM_HERE,
-          base::Bind(&SystemInfoProvider<T>::QueryOnWorkerPool,
-                     base::Unretained(this)),
+          base::Bind(&SystemInfoProvider<T>::QueryOnWorkerPool, this),
           base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN);
   }
 
+ protected:
   // Query the system information synchronously and output the result to the
   // |info| parameter. The |info| contents MUST be reset firstly in its
   // platform specific implementation. Return true if it succeeds, otherwise
   // false is returned.
   virtual bool QueryInfo(T* info) = 0;
 
- protected:
   virtual void QueryOnWorkerPool() {
     bool success = QueryInfo(&info_);
     content::BrowserThread::PostTask(content::BrowserThread::UI, FROM_HERE,
-        base::Bind(&SystemInfoProvider<T>::OnQueryCompleted,
-        base::Unretained(this), success));
+        base::Bind(&SystemInfoProvider<T>::OnQueryCompleted, this, success));
   }
 
   // Called on UI thread. The |success| parameter means whether it succeeds
   // to get the information.
   virtual void OnQueryCompleted(bool success) {
     DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
     while (!callbacks_.empty()) {
       QueryInfoCompletionCallback callback = callbacks_.front();
       callback.Run(info_, success);
@@ skipping 37 matching lines @@
 };
 
 // Static member intialization.
 template<class T>
 typename base::LazyInstance<scoped_refptr<SystemInfoProvider<T> > >
   SystemInfoProvider<T>::single_shared_provider_ = LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SYSTEM_INFO_PROVIDER_H_