Split up ios/web:test_support.

ios/web/public/test/response_providers/error_page_response_provider.h

-// 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.
-
-#ifndef IOS_WEB_PUBLIC_TEST_RESPONSE_PROVIDERS_ERROR_PAGE_RESPONSE_PROVIDER_H_
-#define IOS_WEB_PUBLIC_TEST_RESPONSE_PROVIDERS_ERROR_PAGE_RESPONSE_PROVIDER_H_
-
-#include <map>
-#include <string>
-
-#import "ios/web/public/test/response_providers/html_response_provider.h"
-#include "url/gurl.h"
-
-// A HtmlResponseProvider that supports the following additional URLs:
-// - GetRedirectToDnsFailureUrl - the response is a redirect to
-//   |GetDnsFailureUrl|.
-// - GetDnsFailureUrl - triggers a DNS error.
-class ErrorPageResponseProvider : public HtmlResponseProvider {
- public:
-  ErrorPageResponseProvider() : HtmlResponseProvider() {}
-  explicit ErrorPageResponseProvider(
-      const std::map<GURL, std::string>& responses)
-      : HtmlResponseProvider(responses) {}
-  // Returns a URL that causes a DNS failure.
-  static GURL GetDnsFailureUrl();
-  // Returns a URL that redirects to a bad URL.
-  static GURL GetRedirectToDnsFailureUrl();
-
-  // HtmlResponseProvider implementation.
-  bool CanHandleRequest(const Request& request) override;
-  void GetResponseHeadersAndBody(
-      const Request& request,
-      scoped_refptr<net::HttpResponseHeaders>* headers,
-      std::string* response_body) override;
-};
-
-#endif  // IOS_WEB_PUBLIC_TEST_RESPONSE_PROVIDERS_ERROR_PAGE_RESPONSE_PROVIDER_H_