Supervised user blacklist: Add downloader class to download a blacklist if needed.

chrome/browser/supervised_user/experimental/supervised_user_blacklist_downloader.cc

+// Copyright 2014 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 "chrome/browser/supervised_user/experimental/supervised_user_blacklist_downloader.h"
+
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/logging.h"
+#include "content/public/browser/browser_thread.h"
+#include "net/base/load_flags.h"
+#include "net/http/http_status_code.h"
+#include "net/url_request/url_fetcher.h"
+#include "url/gurl.h"
+
+using content::BrowserThread;
+using net::URLFetcher;
+
+const int kNumRetries = 1;
+
+SupervisedUserBlacklistDownloader::SupervisedUserBlacklistDownloader(
+    const GURL& url,
+    const base::FilePath& path,
+    net::URLRequestContextGetter* request_context,
+    const DownloadFinishedCallback& callback)
+    : callback_(callback),
+      fetcher_(URLFetcher::Create(url, URLFetcher::GET, this)),
+      weak_ptr_factory_(this) {
+  fetcher_->SetRequestContext(request_context);
+  fetcher_->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
+                         net::LOAD_DO_NOT_SAVE_COOKIES |
+                         net::LOAD_IS_DOWNLOAD);
+  fetcher_->SetAutomaticallyRetryOnNetworkChanges(kNumRetries);
+  fetcher_->SaveResponseToFileAtPath(
+      path,
+      BrowserThread::GetMessageLoopProxyForThread(BrowserThread::FILE));
+
+  base::PostTaskAndReplyWithResult(
+      BrowserThread::GetBlockingPool(),
+      FROM_HERE,
+      base::Bind(&base::PathExists, path),
+      base::Bind(&SupervisedUserBlacklistDownloader::OnFileExistsCheckDone,
+                 weak_ptr_factory_.GetWeakPtr()));
+}
+
+SupervisedUserBlacklistDownloader::~SupervisedUserBlacklistDownloader() {}
+
+void SupervisedUserBlacklistDownloader::OnURLFetchComplete(
+    const net::URLFetcher* source) {
+  DCHECK_EQ(fetcher_.get(), source);
+
+  const net::URLRequestStatus& status = source->GetStatus();
+  if (!status.is_success()) {
+    DLOG(WARNING) << "URLRequestStatus error " << status.error();
+    callback_.Run(false);
+    return;
+  }
+
+  int response_code = source->GetResponseCode();
+  if (response_code != net::HTTP_OK) {
+    DLOG(WARNING) << "HTTP error " << response_code;
+    callback_.Run(false);
+    return;
+  }
+
+  // Take ownership of the new file.
+  base::FilePath response_path;
+  bool success = source->GetResponseAsFilePath(true, &response_path);
+  callback_.Run(success);
+}
+
+void SupervisedUserBlacklistDownloader::OnFileExistsCheckDone(bool exists) {
+  if (exists) {
+    // TODO(treib): Figure out a strategy for updating the file.
+    callback_.Run(true);
+  } else {
+    fetcher_->Start();
+  }
+}