Upstream ErrorPageResponseProvider to be used in integration tests.

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>
+
+#include "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_