Don't derive from ChromeURLDataManager::DataSource, and instead have these classes implement a dele…

chrome/browser/ui/webui/chrome_url_data_manager.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_UI_WEBUI_CHROME_URL_DATA_MANAGER_H_
 #define CHROME_BROWSER_UI_WEBUI_CHROME_URL_DATA_MANAGER_H_
 
 #include <string>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/synchronization/lock.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 
 class ChromeURLDataManagerBackend;
 class MessageLoop;
 class Profile;
 
 namespace base {
 class DictionaryValue;
 class RefCountedMemory;
 }
 
+namespace content {
+class URLDataSourceDelegate;
+}
+
+class URLDataSource;
+
 // To serve dynamic data off of chrome: URLs, implement the
 // ChromeURLDataManager::DataSource interface and register your handler
 // with AddDataSource. DataSources must be added on the UI thread (they are also
 // deleted on the UI thread). Internally the DataSources are maintained by
 // ChromeURLDataManagerBackend, see it for details.
 class ChromeURLDataManager : public ProfileKeyedService {
  public:
-  class DataSource;
-
-  // Trait used to handle deleting a DataSource. Deletion happens on the UI
-  // thread.
-  //
-  // Implementation note: the normal shutdown sequence is for the UI loop to
-  // stop pumping events then the IO loop and thread are stopped. When the
-  // DataSources are no longer referenced (which happens when IO thread stops)
-  // they get added to the UI message loop for deletion. But because the UI loop
-  // has stopped by the time this happens the DataSources would be leaked.
-  //
-  // To make sure DataSources are properly deleted ChromeURLDataManager manages
-  // deletion of the DataSources.  When a DataSource is no longer referenced it
-  // is added to |data_sources_| and a task is posted to the UI thread to handle
-  // the actual deletion. During shutdown |DeleteDataSources| is invoked so that
-  // all pending DataSources are properly deleted.
-  struct DeleteDataSource {
-    static void Destruct(const DataSource* data_source) {
-      ChromeURLDataManager::DeleteDataSource(data_source);
-    }
-  };
-
-  // A DataSource is an object that can answer requests for data
-  // asynchronously. DataSources are collectively owned with refcounting smart
-  // pointers and should never be deleted on the IO thread, since their calls
-  // are handled almost always on the UI thread and there's a possibility of a
-  // data race.  The |DeleteDataSource| trait above is used to enforce this.
-  //
-  // An implementation of DataSource should handle calls to
-  // StartDataRequest() by starting its (implementation-specific) asynchronous
-  // request for the data, then call SendResponse() to notify.
-  class DataSource : public base::RefCountedThreadSafe<
-      DataSource, DeleteDataSource> {
-   public:
-    // See source_name_ and message_loop_ below for docs on these parameters.
-    DataSource(const std::string& source_name, MessageLoop* message_loop);
-
-    // Sent by the DataManager to request data at |path|.  The source should
-    // call SendResponse() when the data is available or if the request could
-    // not be satisfied.
-    virtual void StartDataRequest(const std::string& path,
-                                  bool is_incognito,
-                                  int request_id) = 0;
-
-    // Return the mimetype that should be sent with this response, or empty
-    // string to specify no mime type.
-    virtual std::string GetMimeType(const std::string& path) const = 0;
-
-    // Report that a request has resulted in the data |bytes|.
-    // If the request can't be satisfied, pass NULL for |bytes| to indicate
-    // the request is over.
-    virtual void SendResponse(int request_id, base::RefCountedMemory* bytes);
-
-    // Returns the MessageLoop on which the DataSource wishes to have
-    // StartDataRequest called to handle the request for |path|.  If the
-    // DataSource does not care which thread StartDataRequest is called on,
-    // this should return NULL.  The default implementation always returns
-    // message_loop_, which generally results in processing on the UI thread.
-    // It may be beneficial to return NULL for requests that are safe to handle
-    // directly on the IO thread.  This can improve performance by satisfying
-    // such requests more rapidly when there is a large amount of UI thread
-    // contention.
-    virtual MessageLoop* MessageLoopForRequestPath(const std::string& path)
-        const;
-
-    const std::string& source_name() const { return source_name_; }
-
-    // Returns true if this DataSource should replace an existing DataSource
-    // with the same name that has already been registered. The default is
-    // true.
-    //
-    // WARNING: this is invoked on the IO thread.
-    //
-    // TODO: nuke this and convert all callers to not replace.
-    virtual bool ShouldReplaceExistingSource() const;
-
-    // Returns true if responses from this DataSource can be cached.
-    virtual bool AllowCaching() const;
-
-    static void SetFontAndTextDirection(
-        base::DictionaryValue* localized_strings);
-
-   protected:
-    virtual ~DataSource();
-
-   private:
-    friend class ChromeURLDataManagerBackend;
-    friend class ChromeURLDataManager;
-    friend class base::DeleteHelper<DataSource>;
-
-    // SendResponse invokes this on the IO thread. Notifies the backend to
-    // handle the actual work of sending the data.
-    virtual void SendResponseOnIOThread(
-        int request_id,
-        scoped_refptr<base::RefCountedMemory> bytes);
-
-    // The name of this source.
-    // E.g., for favicons, this could be "favicon", which results in paths for
-    // specific resources like "favicon/34" getting sent to this source.
-    const std::string source_name_;
-
-    // The MessageLoop for the thread where this DataSource lives.
-    // Used to send messages to the DataSource.
-    MessageLoop* message_loop_;
-
-    // This field is set and maintained by ChromeURLDataManagerBackend. It is
-    // set when the DataSource is added, and unset if the DataSource is removed.
-    // A DataSource can be removed in two ways: the ChromeURLDataManagerBackend
-    // is deleted, or another DataSource is registered with the same
-    // name. backend_ should only be accessed on the IO thread.
-    // This reference can't be via a scoped_refptr else there would be a cycle
-    // between the backend and data source.
-    ChromeURLDataManagerBackend* backend_;
-  };
-
   explicit ChromeURLDataManager(
       const base::Callback<ChromeURLDataManagerBackend*(void)>& backend);
   virtual ~ChromeURLDataManager();
 
   // Adds a DataSource to the collection of data sources. This *must* be invoked
   // on the UI thread.
   //
   // If |AddDataSource| is called more than once for a particular name it will
   // release the old |DataSource|, most likely resulting in it getting deleted
   // as there are no other references to it. |DataSource| uses the
   // |DeleteOnUIThread| trait to insure that the destructor is called on the UI
   // thread. This is necessary as some |DataSource|s notably |FileIconSource|
   // and |FaviconSource|, have members that will DCHECK if they are not
   // destructed in the same thread as they are constructed (the UI thread).
-  void AddDataSource(DataSource* source);
+  void AddDataSource(URLDataSource* source);
 
   // Deletes any data sources no longer referenced. This is normally invoked
   // for you, but can be invoked to force deletion (such as during shutdown).
   static void DeleteDataSources();
 
   // Convenience wrapper function to add |source| to |profile|'s
   // |ChromeURLDataManager|.
-  static void AddDataSource(Profile* profile, DataSource* source);
+  static void AddDataSource(Profile* profile,
+                            content::URLDataSourceDelegate* delegate);
 
  private:
-  typedef std::vector<const ChromeURLDataManager::DataSource*> DataSources;
+  friend class URLDataSource;
+  friend struct DeleteURLDataSource;
+  typedef std::vector<const URLDataSource*> URLDataSources;
 
   // If invoked on the UI thread the DataSource is deleted immediatlye,
   // otherwise it is added to |data_sources_| and a task is scheduled to handle
   // deletion on the UI thread. See note abouve DeleteDataSource for more info.
-  static void DeleteDataSource(const DataSource* data_source);
+  static void DeleteDataSource(const URLDataSource* data_source);
 
   // Returns true if |data_source| is scheduled for deletion (|DeleteDataSource|
   // was invoked).
-  static bool IsScheduledForDeletion(const DataSource* data_source);
+  static bool IsScheduledForDeletion(const URLDataSource* data_source);
 
   // A callback that returns the ChromeURLDataManagerBackend. Only accessible on
   // the IO thread. This is necessary because ChromeURLDataManager is created on
   // the UI thread, but ChromeURLDataManagerBackend lives on the IO thread.
   const base::Callback<ChromeURLDataManagerBackend*(void)> backend_;
 
   // |data_sources_| that are no longer referenced and scheduled for deletion.
   // Protected by g_delete_lock in the .cc file.
-  static DataSources* data_sources_;
+  static URLDataSources* data_sources_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeURLDataManager);
 };
 
+// Trait used to handle deleting a URLDataSource. Deletion happens on the UI
+// thread.
+//
+// Implementation note: the normal shutdown sequence is for the UI loop to
+// stop pumping events then the IO loop and thread are stopped. When the
+// URLDataSources are no longer referenced (which happens when IO thread stops)
+// they get added to the UI message loop for deletion. But because the UI loop
+// has stopped by the time this happens the URLDataSources would be leaked.
+//
+// To make sure URLDataSources are properly deleted ChromeURLDataManager manages
+// deletion of the URLDataSources.  When a URLDataSource is no longer referenced
+// it is added to |data_sources_| and a task is posted to the UI thread to
+// handle the actual deletion. During shutdown |DeleteDataSources| is invoked so
+// that all pending URLDataSources are properly deleted.
+struct DeleteURLDataSource {
+  static void Destruct(const URLDataSource* data_source) {
+    ChromeURLDataManager::DeleteDataSource(data_source);
+  }
+};
+
+// A URLDataSource is an object that can answer requests for data
+// asynchronously. URLDataSources are collectively owned with refcounting smart
+// pointers and should never be deleted on the IO thread, since their calls
+// are handled almost always on the UI thread and there's a possibility of a
+// data race.  The |DeleteDataSource| trait above is used to enforce this.
+//
+// A delegate of URLDataSource should handle calls to StartDataRequest() by
+// starting its (implementation-specific) asynchronous request for the data,
+// then call SendResponse() to notify.
+class URLDataSource : public base::RefCountedThreadSafe<
+    URLDataSource, DeleteURLDataSource> {
+ public:
+  // See source_name_ below for docs on that parameter. Takes ownership of
+  // |delegate|.
+  URLDataSource(const std::string& source_name,
+                content::URLDataSourceDelegate* delegate);
+
+  // Report that a request has resulted in the data |bytes|.
+  // If the request can't be satisfied, pass NULL for |bytes| to indicate
+  // the request is over.
+  virtual void SendResponse(int request_id, base::RefCountedMemory* bytes);
+
+  const std::string& source_name() const { return source_name_; }
+  content::URLDataSourceDelegate* delegate() const { return delegate_.get(); }
+
+  static void SetFontAndTextDirection(
+      base::DictionaryValue* localized_strings);
+
+ protected:
+  virtual ~URLDataSource();
+
+  content::URLDataSourceDelegate* release_delegate() {
+    return delegate_.release();
+  }
+
+ private:
+  friend class ChromeURLDataManagerBackend;
+  friend class ChromeURLDataManager;
+  friend class base::DeleteHelper<URLDataSource>;
+
+  // SendResponse invokes this on the IO thread. Notifies the backend to
+  // handle the actual work of sending the data.
+  virtual void SendResponseOnIOThread(
+      int request_id,
+      scoped_refptr<base::RefCountedMemory> bytes);
+
+  // The name of this source.
+  // E.g., for favicons, this could be "favicon", which results in paths for
+  // specific resources like "favicon/34" getting sent to this source.
+  const std::string source_name_;
+
+  // This field is set and maintained by ChromeURLDataManagerBackend. It is
+  // set when the DataSource is added, and unset if the DataSource is removed.
+  // A DataSource can be removed in two ways: the ChromeURLDataManagerBackend
+  // is deleted, or another DataSource is registered with the same
+  // name. backend_ should only be accessed on the IO thread.
+  // This reference can't be via a scoped_refptr else there would be a cycle
+  // between the backend and data source.
+  ChromeURLDataManagerBackend* backend_;
+
+  scoped_ptr<content::URLDataSourceDelegate> delegate_;
+};
+
 #endif  // CHROME_BROWSER_UI_WEBUI_CHROME_URL_DATA_MANAGER_H_