Adding status info to DownloadUIItem and piping it through.

components/offline_pages/core/downloads/BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 static_library("offline_pages_ui_adapter") {
   sources = [
@@ skipping 21 matching lines @@
     "download_ui_adapter_unittest.cc",
   ]
 
   deps = [
     ":offline_pages_ui_adapter",
     "//base",
     "//base/test:test_support",
     "//components/offline_pages/core",
     "//components/offline_pages/core:test_support",
     "//components/offline_pages/core/background:background_offliner",
+    "//components/offline_pages/core/background:test_support",
     "//testing/gtest",
   ]
 }