Add a new SyncedTabDelegate for Android.

chrome/browser/sync/glue/session_model_associator.cc

 // Copyright 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 "chrome/browser/sync/glue/session_model_associator.h"
 
 #include <algorithm>
 #include <set>
 #include <utility>
 
@@ skipping 195 matching lines @@
             sync_pb::SessionWindow_BrowserType_TYPE_POPUP);
       }
 
       // Store the order of tabs.
       bool found_tabs = false;
       for (int j = 0; j < (*i)->GetTabCount(); ++j) {
         SessionID::id_type tab_id = (*i)->GetTabIdAt(j);
 
         if (reload_tabs) {
           SyncedTabDelegate* tab = (*i)->GetTabAt(j);
-          // It's possible for GetTabAt to return a null tab if it's not in
-          // memory. We can assume this means the tab already existed but hasn't
-          // changed, so no need to reassociate.
-          if (tab && !AssociateTab(*tab, error)) {
+          // It's possible for GetTabAt to return a tab which has no web
+          // contents. We can assume this means the tab already existed but
+          // hasn't changed, so no need to reassociate.
+          if (tab->HasWebContents() && !AssociateTab(*tab, error)) {
             // Association failed. Either we need to re-associate, or this is an
             // unrecoverable error.
             return false;
           }
         }
 
         // If the tab is valid, it would have been added to the tracker either

[Yaron, 2013/05/30 00:47:23]

Does this logic still work with the changing tab id? I'm concerned that if we
change the tab id and the sessionchangeprocessor doesn't get any navigation
(cause tab is gone) then we're in trouble. That said, this happens when the tab
goes to background so maybe it's ok?

[shashi, 2013/05/30 00:56:14]

Discussed offline, this should work similar to Desktop, on prerender web
contents are swapped and destruction of old web contents should trigger
reassociation.

On 2013/05/30 00:47:23, Yaron wrote:

         // by the above AssociateTab call (at association time), or by the
         // change processor calling AssociateTab for all modified tabs.
         // Therefore, we can key whether this window has valid tabs based on
         // the tab's presence in the tracker.
         const SessionTab* tab = NULL;
         if (synced_session_tracker_.LookupSessionTab(local_tag, tab_id, &tab)) {
           found_tabs = true;
           window_s.add_tab(tab_id);
         }
       }
@@ skipping 908 matching lines @@
 
 bool SessionModelAssociator::CryptoReadyIfNecessary() {
   // We only access the cryptographer while holding a transaction.
   syncer::ReadTransaction trans(FROM_HERE, sync_service_->GetUserShare());
   const syncer::ModelTypeSet encrypted_types = trans.GetEncryptedTypes();
   return !encrypted_types.Has(SESSIONS) ||
          sync_service_->IsCryptographerReady(&trans);
 }
 
 }  // namespace browser_sync