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

chrome/browser/sync/profile_sync_service_mock.h

Index: chrome/browser/sync/profile_sync_service_mock.h
diff --git a/chrome/browser/sync/profile_sync_service_mock.h b/chrome/browser/sync/profile_sync_service_mock.h
index 830827250d9d39ef57e8d8f024e00b086042a9a4..43ea783ea2c0db057b1b4d90548083b0e84d1ebe 100644
--- a/chrome/browser/sync/profile_sync_service_mock.h
+++ b/chrome/browser/sync/profile_sync_service_mock.h
@@ -96,8 +96,8 @@ class ProfileSyncServiceMock : public ProfileSyncService {
       const syncer::SyncProtocolError&));
   MOCK_METHOD1(SetSetupInProgress, void(bool));
 
-  MOCK_METHOD0(GetSessionModelAssociator,
-               browser_sync::SessionModelAssociator*());
+  MOCK_METHOD0(GetOpenTabsUIDelegate,
+               browser_sync::OpenTabsUIDelegate*());
   MOCK_CONST_METHOD0(GetAllSignedInDevicesMock,
                      std::vector<browser_sync::DeviceInfo*>* ());
   // This is to get around the fact that GMOCK does not handle Scoped*.