Componentize PrefSyncableService and support classes.

Create components/syncable_prefs and move PrefSyncableService files,
the support code and the unit tests.

BUG=522544,522537,522536,522532,522530,522527,522526

Review URL: https://codereview.chromium.org/1305213009

Cr-Commit-Position: refs/heads/master@{#349098}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 59ea9d9..cefe99b 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -291,6 +291,7 @@
       "//components/safe_json",
       "//components/sessions",
       "//components/storage_monitor",
+      "//components/syncable_prefs",
       "//components/translate/content/browser",
       "//components/upload_list",
       "//components/url_matcher",
@@ -1040,8 +1041,6 @@
     "password_manager/password_manager_test_base.h",
     "password_manager/test_password_store_service.cc",
     "password_manager/test_password_store_service.h",
-    "prefs/pref_service_mock_factory.cc",
-    "prefs/pref_service_mock_factory.h",
     "profile_resetter/profile_resetter_test_base.cc",
     "profile_resetter/profile_resetter_test_base.h",
     "search_engines/template_url_service_factory_test_util.cc",
@@ -1085,6 +1084,7 @@
     "//components/invalidation/impl:test_support",
     "//components/password_manager/core/browser:test_support",
     "//components/search_engines:test_support",
+    "//components/syncable_prefs:test_support",
     "//components/user_prefs/tracked:user_prefs_tracked_test_support",
     "//content/test:test_support",
     "//chrome/app/theme:theme_resources",