Persist sessionStorage on disk.

content/browser/browser_context.cc

 // 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.
 
 #include "content/public/browser/browser_context.h"
 
 #include "content/browser/appcache/chrome_appcache_service.h"
 #include "content/browser/dom_storage/dom_storage_context_impl.h"
 #include "content/browser/download/download_file_manager.h"
 #include "content/browser/download/download_manager_impl.h"
@@ skipping 68 matching lines @@
 
   scoped_refptr<DatabaseTracker> db_tracker = new DatabaseTracker(
       context->GetPath(), context->IsOffTheRecord(),
       context->GetSpecialStoragePolicy(), quota_manager->proxy(),
       BrowserThread::GetMessageLoopProxyForThread(BrowserThread::FILE));
   context->SetUserData(kDatabaseTrackerKeyName,
                        new UserDataAdapter<DatabaseTracker>(db_tracker));
 
   FilePath path = context->IsOffTheRecord() ? FilePath() : context->GetPath();
   scoped_refptr<DOMStorageContextImpl> dom_storage_context =
-      new DOMStorageContextImpl(path, context->GetSpecialStoragePolicy());
+      new DOMStorageContextImpl(path, context->GetSpecialStoragePolicy(),
+                                context->ShouldSaveSessionStorageOnDisk());

[jam, 2012/07/11 15:51:35]

how about instead of adding a method to the BrowserContext API (which I've tried
to keep minimal), you add a setter for this on content::DOMStorageContext? that
interface already has a method related to session restore.

so kind of like how it's done for cookies: 
http://code.google.com/searchframe#OAMlx_jo-ck/src/chrome/browser/profiles/pr...

[jochen (gone - plz use gerrit), 2012/07/11 17:52:16]

Cookies are a bad role model here: in contrast to all other storage APIs, the
embedder has to provide a persistent store for cookies.

Everything else persists stuff to disk iff the browser context has a path
defined.

The situation here is that an embedder might want to provide a path to have
regular data stored on disk, but would prefer not to persist sessionStorage.
This is different from the flag that is passed to the cookie monster (or the
other storage systems) that just controls how shutdown/startup is handled, but
doesn't change whether a file backend is created or not.

The problem with setting this flag on the DOM storage context directly is that
it needs to be passed to the constructor. The DOM storage context, however, is
created lazily. The embedder would need to invoke this method early enough,
requiring detailed information on how the browser context is implemented.

[jam, 2012/07/11 21:40:28]

I see. It seems that this can be changed so that it's not required at
construction, but just has to be set before it's used? i.e. it's the embedder
who creates a BrowserContext, so if they want to set this, they can do so soon
after before they use it.

[marja, 2012/07/12 09:22:03]

Done.

   context->SetUserData(
       kDOMStorageContextKeyName,
       new UserDataAdapter<DOMStorageContextImpl>(dom_storage_context));
 
   scoped_refptr<IndexedDBContext> indexed_db_context = new IndexedDBContextImpl(
       path, context->GetSpecialStoragePolicy(), quota_manager->proxy(),
       BrowserThread::GetMessageLoopProxyForThread(
           BrowserThread::WEBKIT_DEPRECATED));
   context->SetUserData(
       kIndexedDBContextKeyName,
@@ skipping 161 matching lines @@
                    GetDatabaseTracker(this)));
   }
 
   if (GetUserData(kDOMStorageContextKeyName))
     GetDOMStorageContextImpl(this)->Shutdown();
 
   if (GetUserData(kDownloadManagerKeyName))
     GetDownloadManager(this)->Shutdown();
 }
 
+bool BrowserContext::ShouldSaveSessionStorageOnDisk() const {
+  return false;
+}
+
 }  // namespace content