Upstream ErrorPageResponseProvider to be used in integration tests.

ios/web/BUILD.gn

 # Copyright 2015 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.
 
 import("//ios/build/config.gni")
 import("//ios/web/js_compile.gni")
 import("//testing/test.gni")
 import("//tools/grit/grit_rule.gni")
 
 source_set("web") {
@@ skipping 324 matching lines @@
     "public/test/http_server.h",
     "public/test/http_server.mm",
     "public/test/http_server_util.h",
     "public/test/http_server_util.mm",
     "public/test/js_test_util.h",
     "public/test/js_test_util.mm",
     "public/test/navigation_test_util.h",
     "public/test/navigation_test_util.mm",
     "public/test/response_providers/data_response_provider.h",
     "public/test/response_providers/data_response_provider.mm",
+    "public/test/response_providers/error_page_response_provider.h",
+    "public/test/response_providers/error_page_response_provider.mm",
     "public/test/response_providers/file_based_response_provider.h",
     "public/test/response_providers/file_based_response_provider.mm",
     "public/test/response_providers/file_based_response_provider_impl.h",
     "public/test/response_providers/file_based_response_provider_impl.mm",
     "public/test/response_providers/html_response_provider.h",
     "public/test/response_providers/html_response_provider.mm",
     "public/test/response_providers/html_response_provider_impl.h",
     "public/test/response_providers/html_response_provider_impl.mm",
     "public/test/response_providers/response_provider.h",
     "public/test/response_providers/response_provider.mm",
@@ skipping 210 matching lines @@
 }
 
 grit("resources") {
   source = "ios_web_resources.grd"
   use_qualified_include = true
   outputs = [
     "grit/ios_web_resources.h",
     "ios_web_resources.pak",
   ]
 }