[Sync] Rename syncable_prefs to sync_preferences.

ios/chrome/browser/browser_state/chrome_browser_state_impl.h

Index: ios/chrome/browser/browser_state/chrome_browser_state_impl.h
diff --git a/ios/chrome/browser/browser_state/chrome_browser_state_impl.h b/ios/chrome/browser/browser_state/chrome_browser_state_impl.h
index 990fcb3f8e6fa59a1e707a75b7e5592c783eec4b..54d5292c68d14f3f589a4b742ca01de26dca4f1f 100644
--- a/ios/chrome/browser/browser_state/chrome_browser_state_impl.h
+++ b/ios/chrome/browser/browser_state/chrome_browser_state_impl.h
@@ -15,7 +15,7 @@ namespace ssl_config {
 class SSLConfigServiceManager;
 }
 
-namespace syncable_prefs {
+namespace sync_preferences {
 class PrefServiceSyncable;
 }
 
@@ -80,8 +80,8 @@ class ChromeBrowserStateImpl : public ios::ChromeBrowserState {
   // Keep |prefs_| on top for destruction order because |io_data_| and others
   // store pointers to |prefs_| and shall be destructed first.
   scoped_refptr<user_prefs::PrefRegistrySyncable> pref_registry_;
-  std::unique_ptr<syncable_prefs::PrefServiceSyncable> prefs_;
-  std::unique_ptr<syncable_prefs::PrefServiceSyncable> otr_prefs_;
+  std::unique_ptr<sync_preferences::PrefServiceSyncable> prefs_;
+  std::unique_ptr<sync_preferences::PrefServiceSyncable> otr_prefs_;
   std::unique_ptr<ChromeBrowserStateImplIOData::Handle> io_data_;
 
   std::unique_ptr<PrefProxyConfigTracker> pref_proxy_config_tracker_;