Split up ios/web:test_support.

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

-// 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/web/public/test/response_providers/file_based_response_provider_impl.h"
-
-#include "base/files/file_util.h"
-#import "ios/web/public/test/response_providers/response_provider.h"
-#include "url/gurl.h"
-
-namespace web {
-
-FileBasedResponseProviderImpl::FileBasedResponseProviderImpl(
-    const base::FilePath& path)
-    : path_(path) {}
-
-FileBasedResponseProviderImpl::~FileBasedResponseProviderImpl() {}
-
-bool FileBasedResponseProviderImpl::CanHandleRequest(
-    const ResponseProvider::Request& request) {
-  return base::PathExists(BuildTargetPath(request.url));
-}
-
-base::FilePath FileBasedResponseProviderImpl::BuildTargetPath(const GURL& url) {
-  base::FilePath result = path_;
-  const std::string kLocalhostHost = "localhost";
-  if (url.host() != kLocalhostHost) {
-    result = result.Append(url.host());
-  }
-  std::string url_path = url.path();
-  // Remove the leading slash in url path.
-  if (url_path.length() > 0 && url_path[0] == '/') {
-    url_path.erase(0, 1);
-  }
-  if (!url_path.empty())
-    result = result.Append(url_path);
-  return result;
-}
-
-}  // namespace web