[Sync] Convert SyncSessionSnapshot to a copy-able class.

chrome/browser/sync/profile_sync_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/sync/profile_sync_service.h"
 
 #include <cstddef>
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 1215 matching lines @@
 }
 
 sync_api::UserShare* ProfileSyncService::GetUserShare() const {
   if (backend_.get() && backend_initialized_) {
     return backend_->GetUserShare();
   }
   NOTREACHED();
   return NULL;
 }
 
-const browser_sync::sessions::SyncSessionSnapshot*
+browser_sync::sessions::SyncSessionSnapshot
     ProfileSyncService::GetLastSessionSnapshot() const {
   if (backend_.get() && backend_initialized_) {
     return backend_->GetLastSessionSnapshot();
   }
   NOTREACHED();
-  return NULL;
+  return browser_sync::sessions::SyncSessionSnapshot();
 }
 
 bool ProfileSyncService::HasUnsyncedItems() const {
   if (backend_.get() && backend_initialized_) {
     return backend_->HasUnsyncedItems();
   }
   NOTREACHED();
   return false;
 }
 
@@ skipping 401 matching lines @@
   // See http://stackoverflow.com/questions/6224121/is-new-this-myclass-undefined-behaviour-after-directly-calling-the-destru.
   ProfileSyncService* old_this = this;
   this->~ProfileSyncService();
   new(old_this) ProfileSyncService(
       new ProfileSyncComponentsFactoryImpl(profile,
                                            CommandLine::ForCurrentProcess()),
       profile,
       signin,
       behavior);
 }