Implement DatabaseQuotaClient's DeteleteOriginData method.

webkit/quota/quota_task.h

 // Copyright (c) 2011 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 WEBKIT_QUOTA_QUOTA_TASK_H_
 #define WEBKIT_QUOTA_QUOTA_TASK_H_
 #pragma once
 
 #include <set>
 
@@ skipping 48 matching lines @@
 // For tasks that post tasks to the other thread.
 class QuotaThreadTask : public QuotaTask,
                         public base::RefCountedThreadSafe<QuotaThreadTask> {
  public:
   QuotaThreadTask(QuotaTaskObserver* observer,
                   scoped_refptr<base::MessageLoopProxy> target_message_loop);
 
  protected:
   virtual ~QuotaThreadTask();
 
-  // Called on the target message loop.
-  virtual void RunOnTargetThread() = 0;
+  // One of the following Run methods should be overriden for execution
+  // on the target thread.
+
+  // A task to invoke the CallCompleted() method on the original thread will
+  // be scheduled immediately upon return from RunOnTargetThread().
+  virtual void RunOnTargetThread();
+
+  // A task to invoke the CallCompleted() method on the original thread will
+  // only be scheduled if RunOnTargetThreadAsync returns true. If false is
+  // returned, the derived class should schedule a task to do so upon actual
+  // completion.
+  virtual bool RunOnTargetThreadAsync();
 
   virtual void Run() OVERRIDE;
   scoped_refptr<base::MessageLoopProxy> target_message_loop() const {
     return target_message_loop_;
   }
 
  private:
   friend class base::RefCountedThreadSafe<QuotaThreadTask>;
   friend class QuotaTaskObserver;
   void CallRunOnTargetThread();
@@ skipping 12 matching lines @@
   QuotaTaskObserver();
   void RegisterTask(QuotaTask* task);
   void UnregisterTask(QuotaTask* task);
 
   typedef std::set<QuotaTask*> TaskSet;
   TaskSet running_quota_tasks_;
 };
 }
 
 #endif  // WEBKIT_QUOTA_QUOTA_TASK_H_