Allow SessionService to be disabled.

chrome/browser/sessions/tab_restore_service.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 "chrome/browser/sessions/tab_restore_service.h"
 
 #include <algorithm>
 #include <iterator>
 #include <map>
 
@@ skipping 421 matching lines @@
   }
 
   restoring_ = false;
   NotifyTabsChanged();
 }
 
 void TabRestoreService::LoadTabsFromLastSession() {
   if (load_state_ != NOT_LOADED || entries_.size() == kMaxEntries)
     return;
 
+#if !defined(ENABLE_SESSION_SERVICE)
+  // If sessions are not stored in the SessionService, default to
+  // |LOADED_LAST_SESSION| state.
+  load_state_ = LOADING | LOADED_LAST_SESSION;
+#else
   load_state_ = LOADING;
 
   SessionService* session_service =
       SessionServiceFactory::GetForProfile(profile());
   if (!profile()->restored_last_session() &&
       !profile()->DidLastSessionExitCleanly() &&
       session_service) {
     // The previous session crashed and wasn't restored. Load the tabs/windows
     // that were open at the point of crash from the session service.
     session_service->GetLastSession(
         &crash_consumer_,
         base::Bind(&TabRestoreService::OnGotPreviousSession,
                    base::Unretained(this)));
   } else {
     load_state_ |= LOADED_LAST_SESSION;
   }
+#endif
 
   // Request the tabs closed in the last session. If the last session crashed,
   // this won't contain the tabs/window that were open at the point of the
   // crash (the call to GetLastSession above requests those).
   ScheduleGetLastSessionCommands(
       new InternalGetCommandsRequest(
           base::Bind(&TabRestoreService::OnGotLastSessionCommands,
                      base::Unretained(this))),
       &load_consumer_);
 }
@@ skipping 744 matching lines @@
   // the front, not the end and we just added the entries to the end).
   entries_to_write_ = staging_entries_.size();
 
   PruneEntries();
   NotifyTabsChanged();
 }
 
 Time TabRestoreService::TimeNow() const {
   return time_factory_ ? time_factory_->TimeNow() : Time::Now();
 }