Upstream ErrorPageResponseProvider to be used in integration tests.

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

Index: ios/web/public/test/response_providers/error_page_response_provider.mm
diff --git a/ios/web/public/test/response_providers/error_page_response_provider.mm b/ios/web/public/test/response_providers/error_page_response_provider.mm
new file mode 100644
index 0000000000000000000000000000000000000000..086912c0468590708949f77a79af67ea7b70b82b
--- /dev/null
+++ b/ios/web/public/test/response_providers/error_page_response_provider.mm
@@ -0,0 +1,43 @@
+// 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.
+
+#include "ios/web/public/test/response_providers/error_page_response_provider.h"
+
+#include "base/logging.h"
+#import "ios/web/public/test/http_server.h"
+#include "net/http/http_status_code.h"
+
+// static
+GURL ErrorPageResponseProvider::DNSFailureUrl() {
+  return GURL("http://mock/bad");
+}
+
+// static
+GURL ErrorPageResponseProvider::RedirectToDNSFailureUrl() {
+  return web::test::HttpServer::MakeUrl("http://mock/redirect");
+}
+
+// Returns true for |RedirectToDNSFailureUrl|.
+bool ErrorPageResponseProvider::CanHandleRequest(const Request& request) {
+  if (HtmlResponseProvider::CanHandleRequest(request) ||

[Eugene But (OOO till 7-30), 2016/08/19 21:29:02]

Maybe

return HtmlResponseProvider::CanHandleRequest(request) || request.url ==
ErrorPageResponseProvider::RedirectToDNSFailureUrl();

[baxley, 2016/08/19 22:25:44]

Done.

+      request.url == ErrorPageResponseProvider::RedirectToDNSFailureUrl()) {
+    return true;
+  }
+  return false;
+}
+
+void ErrorPageResponseProvider::GetResponseHeadersAndBody(
+    const Request& request,
+    scoped_refptr<net::HttpResponseHeaders>* headers,
+    std::string* response_body) {
+  if (HtmlResponseProvider::CanHandleRequest(request)) {
+    HtmlResponseProvider::GetResponseHeadersAndBody(request, headers,
+                                                    response_body);
+  } else if (request.url == RedirectToDNSFailureUrl()) {
+    *headers = web::ResponseProvider::GetRedirectResponseHeaders(
+        ErrorPageResponseProvider::DNSFailureUrl().spec(), net::HTTP_FOUND);
+  } else {
+    NOTREACHED();
+  }
+}