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 219 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 null tab or 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 && tab->HasWebContents() && !AssociateTab(*tab, error)) {

[Yaron, 2013/05/21 18:32:07]

I believe the existence-check for tab was purely for the webcontents-less case
on Android. Can't we always ensure that we have a tab now? 

[shashi, 2013/05/21 23:11:21]

Done.

             // 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
         // 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
@@ skipping 907 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