Add Store+Sync to reading list.

ios/chrome/browser/reading_list/BUILD.gn

Index: ios/chrome/browser/reading_list/BUILD.gn
diff --git a/ios/chrome/browser/reading_list/BUILD.gn b/ios/chrome/browser/reading_list/BUILD.gn
index 2450771828da44f3a4e9e22cf6eb34ce104404a2..47831403f12c29227e0740f9b0c211dcb0cbfb3d 100644
--- a/ios/chrome/browser/reading_list/BUILD.gn
+++ b/ios/chrome/browser/reading_list/BUILD.gn
@@ -20,10 +20,11 @@ source_set("reading_list") {
     "reading_list_model_impl.h",
     "reading_list_model_observer.h",
     "reading_list_model_storage.h",
-    "reading_list_model_storage_defaults.h",
-    "reading_list_model_storage_defaults.mm",
     "reading_list_pref_names.cc",
     "reading_list_pref_names.h",
+    "reading_list_store.cc",
+    "reading_list_store.h",
+    "reading_list_store_delegate.h",
     "url_downloader.cc",
     "url_downloader.h",
   ]
@@ -33,8 +34,11 @@ source_set("reading_list") {
     "//components/keyed_service/ios",
     "//components/pref_registry",
     "//components/prefs",
+    "//components/sync",
+    "//components/sync/protocol",
     "//ios/chrome/browser",
     "//ios/chrome/browser/browser_state",
+    "//ios/chrome/browser/reading_list/proto",
     "//ios/web",
     "//net",
     "//url",
@@ -48,16 +52,19 @@ source_set("unit_tests") {
   testonly = true
   sources = [
     "reading_list_entry_unittest.cc",
-    "reading_list_model_storage_unittest.mm",
     "reading_list_model_unittest.cc",
+    "reading_list_store_unittest.cc",
     "url_downloader_unittest.cc",
   ]
   deps = [
     ":reading_list",
     "//base",
     "//base/test:test_support",
+    "//components/sync:test_support_model",
+    "//components/sync/protocol",
     "//ios/chrome/browser",
     "//ios/chrome/browser/dom_distiller",
+    "//ios/chrome/browser/reading_list/proto",
     "//ios/web:test_support",
     "//testing/gtest",
   ]