sync: Add --enable-sync-sessions-v2 and necessary plumbing to use SessionsSyncManager.

chrome/common/chrome_switches.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.
 
 // Defines all the command-line switches used by Chrome.
 
 #ifndef CHROME_COMMON_CHROME_SWITCHES_H_
 #define CHROME_COMMON_CHROME_SWITCHES_H_
 
 #include "build/build_config.h"
@@ skipping 202 matching lines @@
 extern const char kEnableSpdy2[];
 extern const char kDisableSpdy31[];
 extern const char kEnableSpdy4a2[];
 extern const char kEnableSpellingAutoCorrect[];
 extern const char kEnableSpellingServiceFeedback[];
 extern const char kEnableStackedTabStrip[];
 extern const char kEnableStreamlinedHostedApps[];
 extern const char kEnableSuggestionsTabPage[];
 extern const char kEnableSyncArticles[];
 extern const char kEnableSyncSyncedNotifications[];
+extern const char kEnableSyncSessionsV2[];
 extern const char kEnableTabGroupsContextMenu[];
 extern const char kEnableThumbnailRetargeting[];
 extern const char kEnableTranslateNewUX[];
 extern const char kEnableUnrestrictedSSL3Fallback[];
 extern const char kEnableUserAlternateProtocolPorts[];
 extern const char kEnableWatchdog[];
 extern const char kEnableWebSocketOverSpdy[];
 extern const char kExplicitlyAllowedPorts[];
 extern const char kExtensionProcess[];
 extern const char kExtensionsInstallVerification[];
@@ skipping 235 matching lines @@
 #else
 extern const char kEnablePrintPreview[];
 #endif
 
 // DON'T ADD RANDOM STUFF HERE. Put it in the main section above in
 // alphabetical order, or in one of the ifdefs (also in order in each section).
 
 }  // namespace switches
 
 #endif  // CHROME_COMMON_CHROME_SWITCHES_H_