Abstract content::SessionStorageNamespace from core TabRestore code

components/sessions/core/tab_restore_service_client.h

 // Copyright 2015 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 COMPONENTS_SESSIONS_CORE_TAB_RESTORE_SERVICE_CLIENT_H_
 #define COMPONENTS_SESSIONS_CORE_TAB_RESTORE_SERVICE_CLIENT_H_
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
+#include "base/memory/ref_counted.h"
 #include "base/memory/scoped_vector.h"
 #include "components/sessions/session_id.h"
+#include "components/sessions/sessions_export.h"
 
 namespace base {
 class CancelableTaskTracker;
 class SequencedWorkerPool;
 }
 
 // TODO(blundell): Remove all references to WebContents from
 // TabRestoreServiceClient and get rid of this. crbug.com/530174
 namespace content {
 class WebContents;
 }
 
 namespace sessions {
 struct SessionWindow;
 }
 
 class GURL;
 class TabRestoreServiceDelegate;
 
 namespace sessions {
 
 struct SessionWindow;
 
 // Callback from TabRestoreServiceClient::GetLastSession.
 // The second parameter is the id of the window that was last active.
 typedef base::Callback<void(ScopedVector<SessionWindow>, SessionID::id_type)>
     GetLastSessionCallback;
 
+// A class that is used to associate embedder-specific data with
+// TabRestoreService::Tab. See TabRestoreServiceClient::GetClientData().
+class SESSIONS_EXPORT TabClientData : public base::RefCounted<TabClientData> {

[blundell, 2015/09/15 19:38:57]

Note that this class needs to be refcounted because the Tab struct is copied and
assigned all over the place (I should probably put a comment to that effect in
the code...).

[sky, 2015/09/15 21:59:49]

I hate to propagate that. How about a Clone() method on TabClientData?

[blundell, 2015/09/16 11:53:51]

Done.

+ protected:
+  virtual ~TabClientData() {}
+
+ private:
+  friend class base::RefCounted<TabClientData>;
+};
+
 // A client interface that needs to be supplied to the tab restore service by
 // the embedder.
-class TabRestoreServiceClient {
+class SESSIONS_EXPORT TabRestoreServiceClient {
  public:
   virtual ~TabRestoreServiceClient() {}
 
   // Creates a TabRestoreServiceDelegate instance that is associated with
   // |host_desktop_type| and |app_name|. May return nullptr (e.g., if the
   // embedder does not support TabRestoreServiceDelegate functionality).
   // Note that |host_desktop_type| is opaque to the component; the only values
   // that will be passed here are those that have been passed *in* to the
   // component from the embedder via TabRestoreService.
   virtual TabRestoreServiceDelegate* CreateTabRestoreServiceDelegate(
@@ skipping 21 matching lines @@
   virtual bool ShouldTrackURLForRestore(const GURL& url) = 0;
 
   // Returns the extension app ID for the given WebContents, or the empty string
   // if there is no such ID (e.g., if extensions are not supported by the
   // embedder).
   // TODO(blundell): Replace the usage of WebContents here with the cross-
   // platform interface that will abstract it. crbug.com/530174
   virtual std::string GetExtensionAppIDForWebContents(
       content::WebContents* web_contents) = 0;
 
+  // Returns any client data that should be associated with the
+  // TabRestoreService::Tab corresponding to |web_contents|. That tab will own
+  // this reference to the returned data.
+  virtual scoped_refptr<TabClientData> GetTabClientDataForWebContents(
+      content::WebContents* web_contents) = 0;
+
   // Get the sequenced worker pool for running tasks on the backend thread as
   // long as the system is not shutting down.
   virtual base::SequencedWorkerPool* GetBlockingPool() = 0;
 
   // Returns the path of the directory to save state into.
   virtual base::FilePath GetPathToSaveTo() = 0;
 
   // Returns the URL that corresponds to the new tab page.
   virtual GURL GetNewTabURL() = 0;
 
   // Returns whether there is a previous session to load.
   virtual bool HasLastSession() = 0;
 
   // Fetches the contents of the last session, notifying the callback when
   // done. If the callback is supplied an empty vector of SessionWindows
   // it means the session could not be restored.
   virtual void GetLastSession(const GetLastSessionCallback& callback,
                               base::CancelableTaskTracker* tracker) = 0;
 
   // Called when a tab is restored. |url| is the URL that the tab is currently
   // visiting.
   virtual void OnTabRestored(const GURL& url) {}
 };
 
 }  // namespace sessions
 
 #endif  // COMPONENTS_SESSIONS_CORE_TAB_RESTORE_SERVICE_CLIENT_H_