Introduce //components/user_prefs, use to eliminate c/b/prefs dependency in Autofill.

chrome/browser/sync/sync_prefs.cc

Index: chrome/browser/sync/sync_prefs.cc
diff --git a/chrome/browser/sync/sync_prefs.cc b/chrome/browser/sync/sync_prefs.cc
index 4a9f430829495a4e6fc92b4eacfc6c9174db01e8..c3cac438a130381ed09925a166561bad05df437b 100644
--- a/chrome/browser/sync/sync_prefs.cc
+++ b/chrome/browser/sync/sync_prefs.cc
@@ -10,11 +10,11 @@
 #include "base/strings/string_number_conversions.h"
 #include "base/values.h"
 #include "build/build_config.h"
-#include "chrome/browser/prefs/pref_registry_syncable.h"
 #include "chrome/browser/profiles/profile_io_data.h"
 #include "chrome/browser/sync/profile_sync_service.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/pref_names.h"
+#include "components/user_prefs/pref_registry_syncable.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_source.h"