[ios] Never show reading list items for UI refresh phase 1.

The NTP already has a reading list icon with a badged count
when there are unread items so the larger RL collection
items is superfluous.

Bug: 805638
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Ic34ed523bb6946017ec312aca6e6c9c11ac2b2f3
Reviewed-on: https://chromium-review.googlesource.com/947836Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540851}

ios/chrome/browser/ntp_snippets/BUILD.gn

@@ -29,6 +29,7 @@ source_set("ntp_snippets") {
     "//ios/chrome/browser/history",
     "//ios/chrome/browser/reading_list",
     "//ios/chrome/browser/signin",
+    "//ios/chrome/browser/ui:ui_util",
     "//ios/chrome/common",
     "//ios/web",
     "//net",

ios/chrome/browser/ntp_snippets/ios_chrome_content_suggestions_service_factory_util.cc

@@ -44,6 +44,7 @@
 #include "ios/chrome/browser/pref_names.h"
 #include "ios/chrome/browser/reading_list/reading_list_model_factory.h"
 #include "ios/chrome/browser/signin/identity_manager_factory.h"
+#include "ios/chrome/browser/ui/ui_util.h"
 #include "ios/chrome/common/channel_info.h"
 #include "ios/web/public/browser_state.h"
 #include "net/url_request/url_request_context_getter.h"
@@ -139,6 +140,10 @@ std::unique_ptr<KeyedService> CreateChromeContentSuggestionsService(
 
 void RegisterReadingListProvider(ContentSuggestionsService* service,
                                  web::BrowserState* browser_state) {
+  // Prevent loading any reading list items for refresh.
+  if (IsUIRefreshPhase1Enabled())
+    return;
+
   ios::ChromeBrowserState* chrome_browser_state =
       ios::ChromeBrowserState::FromBrowserState(browser_state);