Create a common base class for all the webdatas

chrome/browser/api/webdata/web_data_service_base.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_API_WEBDATA_WEB_DATA_SERVICE_BASE_H_
 #define CHROME_BROWSER_API_WEBDATA_WEB_DATA_SERVICE_BASE_H_
 
+#include "base/files/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_source.h"
+#include "sql/init_status.h"
+
+class WebDatabase;
+class WebDatabaseService;
+
+namespace base {
+class Thread;
+}
 
 // Base for WebDataService class hierarchy.
-class WebDataServiceBase {
+class WebDataServiceBase
+    : public base::RefCountedThreadSafe<WebDataServiceBase,
+          content::BrowserThread::DeleteOnUIThread> {
  public:
   // All requests return an opaque handle of the following type.
   typedef int Handle;
 
-  virtual ~WebDataServiceBase() {}
+  WebDataServiceBase();
 
   // Cancel any pending request. You need to call this method if your
   // WebDataServiceConsumer is about to be deleted.
-  virtual void CancelRequest(Handle h) = 0;
+  virtual void CancelRequest(Handle h);
 
   // Returns the notification source for this service. This may use a
   // pointer other than this object's |this| pointer.
-  virtual content::NotificationSource GetNotificationSource() = 0;
+  virtual content::NotificationSource GetNotificationSource();
+
+  // Shutdown the web data service. The service can no longer be used after this
+  // call.
+  virtual void ShutdownOnUIThread();
+
+  // Initializes the web data service.
+  virtual void Init(const base::FilePath& path);

[Jói, 2013/03/18 14:34:48]

Only one subclass is calling Init, is that how we avoid constructing two
separate WebDatabaseService objects in this change?

[Cait (Slow), 2013/03/18 14:50:15]

Yes. For now, AutofillWebData doesn't make much use of its base class, and
instead calls into the WebDataService received on  construction. 

This does mean that AutofillWebData still needs to override some base methods
though. Adding those now.

+
+  // Unloads the database without actually shutting down the service.  This can
+  // be used to temporarily reduce the browser process' memory footprint.
+  void UnloadDatabase();
+
+  // Unloads the database permanently and shuts down service.
+  void ShutdownDatabase();
+
+  // Returns true if the database load has completetd successfully, and
+  // ShutdownOnUIThread has not yet been called.
+  virtual bool IsDatabaseLoaded();
+
+  // Returns a pointer to the DB (used by SyncableServices). May return NULL if
+  // the database is not loaded or otherwise unavailable. Must be called on
+  // DBThread.
+  virtual WebDatabase* GetDatabase();
+
+ protected:
+  virtual ~WebDataServiceBase();
+
+  // Our database service.
+  scoped_ptr<WebDatabaseService> wdbs_;

[Jói, 2013/03/18 12:36:41]

If I'm reading this right, the next change would introduce a top-level owning
class (e.g. WebDataManager) that would own WebDatabaseService and each of the
XyzWebDataService implementations, and would change AutofillWebDataService to
use the database directly rather than just delegate to WebDataService?

[Cait (Slow), 2013/03/18 13:52:00]

That's correct. The top level class would handle init'ing and shutting down the
db, and pass it into each XYZWebdata for them to use. The one thing i wanted to
confirm with you was that (at least for now) this means we'll have to ref-count
the webdatabaseservice, correct?

On 2013/03/18 12:36:41, Jói wrote:

+
+  // True if we've received a notification that the WebDatabase has loaded.
+  bool db_loaded_;
+
+ private:
+  friend struct content::BrowserThread::DeleteOnThread<
+      content::BrowserThread::UI>;
+  friend class base::DeleteHelper<WebDataServiceBase>;
+
+  void DBInitFailed(sql::InitStatus sql_status);
+  void NotifyDatabaseLoadedOnUIThread();
+  void DatabaseInitOnDB(sql::InitStatus status);
 };
 
 #endif  // CHROME_BROWSER_API_WEBDATA_WEB_DATA_SERVICE_BASE_H_