Rewire the local sync switches through the pref store.

chrome/browser/prefs/chrome_command_line_pref_store.cc

Index: chrome/browser/prefs/chrome_command_line_pref_store.cc
diff --git a/chrome/browser/prefs/chrome_command_line_pref_store.cc b/chrome/browser/prefs/chrome_command_line_pref_store.cc
index bd91955c25a536f3c72b1e1ae897da0128dd1382..9138af4cda134684bd96a2b71341bca8d5aa8d78 100644
--- a/chrome/browser/prefs/chrome_command_line_pref_store.cc
+++ b/chrome/browser/prefs/chrome_command_line_pref_store.cc
@@ -20,12 +20,14 @@
 #include "build/build_config.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
+#include "components/browser_sync/browser_sync_switches.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_switches.h"
 #include "components/proxy_config/proxy_config_dictionary.h"
 #include "components/proxy_config/proxy_config_pref_names.h"
 #include "components/ssl_config/ssl_config_prefs.h"
 #include "components/ssl_config/ssl_config_switches.h"
+#include "components/sync/base/pref_names.h"
 #include "content/public/common/content_switches.h"
 #include "ui/base/ui_base_switches.h"
 #include "ui/display/display_switches.h"
@@ -55,6 +57,7 @@ const CommandLinePrefStore::SwitchToPreferenceMapEntry
 const CommandLinePrefStore::SwitchToPreferenceMapEntry
     ChromeCommandLinePrefStore::path_switch_map_[] = {
       { switches::kDiskCacheDir, prefs::kDiskCacheDir },
+      { switches::kLocalSyncBackendDir, syncer::prefs::kLocalSyncBackendDir },
 };
 
 const CommandLinePrefStore::BooleanSwitchToPreferenceMapEntry
@@ -79,6 +82,8 @@ const CommandLinePrefStore::BooleanSwitchToPreferenceMapEntry
          prefs::kUnifiedDesktopEnabledByDefault, true},
 #endif
         {switches::kUnsafePacUrl, prefs::kPacHttpsUrlStrippingEnabled, false},
+        {switches::kEnableLocalSyncBackend,
+         syncer::prefs::kEnableLocalSyncBackend, false},
 };
 
 const CommandLinePrefStore::SwitchToPreferenceMapEntry