[Sync] Add full history sync experiment

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 913 matching lines @@
     CommandLine::ForCurrentProcess()->AppendSwitch(switches::kSyncTabFavicons);
 #endif
   }
 
   if (experiments.keystore_encryption) {
     about_flags::SetExperimentEnabled(g_browser_process->local_state(),
                                       syncer::kKeystoreEncryptionFlag,
                                       true);
   }
 
+  if (experiments.full_history_sync) {
+    about_flags::SetExperimentEnabled(g_browser_process->local_state(),
+                                      syncer::kFullHistorySyncFlag,
+                                      true);
+  }
+
   current_experiments_ = experiments;
 }
 
 void ProfileSyncService::UpdateAuthErrorState(const AuthError& error) {
   is_auth_in_progress_ = false;
   last_auth_error_ = error;
 
   // Fan the notification out to interested UI-thread components.
   NotifyObservers();
   if (signin())
@@ skipping 1016 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);
 }