Split up ios/web:test_support.

ios/chrome/browser/store_kit/BUILD.gn

 # Copyright 2017 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.
 
 source_set("store_kit") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "store_kit_launcher.h",
     "store_kit_tab_helper.h",
     "store_kit_tab_helper.mm",
   ]
   deps = [
     "//base",
     "//ios/web",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "store_kit_tab_helper_unittest.mm",
   ]
   deps = [
     ":store_kit",
     "//base",
     "//ios/web",
-    "//ios/web:test_support",
+    "//ios/web/public/test",
     "//testing/gtest",
     "//third_party/ocmock:ocmock",
   ]
 }