Use Observer to notify of WebDB load instead of callbacks

components/webdata/common/web_database_observer.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.

[dhollowa, 2013/04/18 16:21:17]

nit: "Copyright 2013"

[Cait (Slow), 2013/04/19 19:06:22]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_WEBDATA_COMMON_WEB_DATABASE_OBSERVER_H_
+#define COMPONENTS_WEBDATA_COMMON_WEB_DATABASE_OBSERVER_H_
+
+#include "sql/init_status.h"
+
+// WebDatabase loads asynchronously on the DB thread. Clients on the UI thread
+// can use this interface to be notified when the load is complete, or if it
+// fails.
+class WebDatabaseObserver {
+ public:
+  // Called when DB has been loaded successfully.
+  virtual void WebDatabaseLoaded() {};

[dhollowa, 2013/04/18 16:21:17]

Could you explain why these are not "= 0"?  I'm ok with it, but I would have
thought it desirable to have compiler support alerting you to classes that say
they're an observer but do nothing.

[Cait (Slow), 2013/04/19 19:06:22]

Several observers want to be told that the DB loaded successfully but don't care
if it failed. We could make the WebDatabaseLoaded() pure virtual, but keep the
WebDatabaseLoadFailed() as is.

+
+  // Called when load failed. |status| contains error code.
+  virtual void WebDatabaseLoadFailed(sql::InitStatus status) {};
+
+ protected:
+  virtual ~WebDatabaseObserver() {}
+};
+
+
+#endif  // COMPONENTS_WEBDATA_COMMON_WEB_DATABASE_OBSERVER_H_