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

chrome/browser/sessions/better_session_restore_browsertest.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 "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/lazy_instance.h"
 #include "base/path_service.h"
 #include "base/prefs/pref_service.h"
@@ skipping 196 matching lines @@
 
   void CheckReloadedPageRestored() {
     CheckTitle(browser(), title_pass_);
   }
 
   void CheckReloadedPageRestored(Browser* browser) {
     CheckTitle(browser, title_pass_);
   }
 
   void CheckReloadedPageNotRestored() {
+    // If only active tabs are loaded, force loading of the tabs.
+    if (SessionRestore::WillLoadActiveTabsOnly()) {
+      for (int i = 0; i < browser()->tab_strip_model()->count(); i++) {
+        content::WebContents* web_contents =
+            browser()->tab_strip_model()->GetWebContentsAt(i);
+        web_contents->GetController().LoadIfNecessary();
+      }
+    }
     CheckReloadedPageNotRestored(browser());
   }
 
   void CheckReloadedPageNotRestored(Browser* browser) {
     CheckTitle(browser, title_storing_);
   }
 
   void CheckTitle(Browser* browser, const base::string16& expected_title) {
     content::WebContents* web_contents =
         browser->tab_strip_model()->GetWebContentsAt(0);
@@ skipping 608 matching lines @@
   CookieSettings::Factory::GetForProfile(new_browser->profile())->
       SetDefaultCookieSetting(CONTENT_SETTING_SESSION_ONLY);
   // ... even if background mode is active.
   EnableBackgroundMode();
   new_browser = QuitBrowserAndRestore(new_browser, true);
   StoreDataWithPage(new_browser, "cookies.html");
   DisableBackgroundMode();
   new_browser = QuitBrowserAndRestore(new_browser, true);
   StoreDataWithPage(new_browser, "cookies.html");
 }