[Session restore] Expose lazy mode and fix browser tests.

chrome/browser/sessions/session_restore.h

 // 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.
 
 #ifndef CHROME_BROWSER_SESSIONS_SESSION_RESTORE_H_
 #define CHROME_BROWSER_SESSIONS_SESSION_RESTORE_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 80 matching lines @@
   // Returns true if synchronously restoring a session.
   static bool IsRestoringSynchronously();
 
   // Registers a callback that is notified every time session restore completes.
   // Note that 'complete' means all the browsers and tabs have been created but
   // have not necessarily finished loading. The integer supplied to the callback
   // indicates the number of tabs that were created.
   static CallbackSubscription RegisterOnSessionRestoredCallback(
       const base::Callback<void(int)>& callback);
 
+  // Returns true if only active tabs are to be loaded during session restore
+  // (lazy load). Otherwise returns false if all tabs will be loaded when
+  // restored.
+  static bool WillLoadActiveTabsOnly();
+
  private:
   SessionRestore();
 
   // Accessor for |*on_session_restored_callbacks_|. Creates a new object the
   // first time so that it always returns a valid object.
   static CallbackList* on_session_restored_callbacks() {
     if (!on_session_restored_callbacks_)
       on_session_restored_callbacks_ = new CallbackList();
     return on_session_restored_callbacks_;
   }
 
   // Contains all registered callbacks for session restore notifications.
   static CallbackList* on_session_restored_callbacks_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionRestore);
 };
 
 #endif  // CHROME_BROWSER_SESSIONS_SESSION_RESTORE_H_