Move most of the component updater artifacts to update_client.

components/update_client/crx_downloader.h

Index: components/update_client/crx_downloader.h
diff --git a/components/update_client/crx_downloader.h b/components/update_client/crx_downloader.h
new file mode 100644
index 0000000000000000000000000000000000000000..661b5c846241ed9fec7a0cc49c8576c90407f94f
--- /dev/null
+++ b/components/update_client/crx_downloader.h
@@ -0,0 +1,156 @@
+// 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.
+
+#ifndef COMPONENTS_UPDATE_CLIENT_CRX_DOWNLOADER_H_
+#define COMPONENTS_UPDATE_CLIENT_CRX_DOWNLOADER_H_
+
+#include <stdint.h>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "url/gurl.h"
+
+namespace base {
+class SequencedTaskRunner;
+class SingleThreadTaskRunner;
+}
+
+namespace net {
+class URLRequestContextGetter;
+}
+
+namespace update_client {
+
+// Defines a download interface for downloading components, with retrying on
+// fallback urls in case of errors. This class implements a chain of
+// responsibility design pattern. It can give successors in the chain a chance
+// to handle a download request, until one of them succeeds, or there are no
+// more urls or successors to try. A callback is always called at the end of
+// the download, one time only.
+// When multiple urls and downloaders exists, first all the urls are tried, in
+// the order they are provided in the StartDownload function argument. After
+// that, the download request is routed to the next downloader in the chain.
+// The members of this class expect to be called from the main thread only.
+class CrxDownloader {
+ public:
+  struct DownloadMetrics {
+    enum Downloader { kNone = 0, kUrlFetcher, kBits };
+
+    DownloadMetrics();
+
+    GURL url;
+
+    Downloader downloader;
+
+    int error;
+
+    int64_t downloaded_bytes;  // -1 means that the byte count is unknown.
+    int64_t total_bytes;
+
+    uint64_t download_time_ms;
+  };
+
+  // Contains the progress or the outcome of the download.
+  struct Result {
+    Result();
+
+    // Download error: 0 indicates success.
+    int error;
+
+    // Path of the downloaded file if the download was successful.
+    base::FilePath response;
+
+    // Number of bytes actually downloaded, not including the bytes downloaded
+    // as a result of falling back on urls.
+    int64_t downloaded_bytes;
+
+    // Number of bytes expected to be downloaded.
+    int64_t total_bytes;
+  };
+
+  // The callback fires only once, regardless of how many urls are tried, and
+  // how many successors in the chain of downloaders have handled the
+  // download. The callback interface can be extended if needed to provide
+  // more visibility into how the download has been handled, including
+  // specific error codes and download metrics.
+  typedef base::Callback<void(const Result& result)> DownloadCallback;
+
+  // The callback may fire 0 or many times during a download. Since this
+  // class implements a chain of responsibility, the callback can fire for
+  // different urls and different downloaders. The number of actual downloaded
+  // bytes is not guaranteed to monotonically increment over time.
+  typedef base::Callback<void(const Result& result)> ProgressCallback;
+
+  // Factory method to create an instance of this class and build the
+  // chain of responsibility. |is_background_download| specifies that a
+  // background downloader be used, if the platform supports it.
+  // |url_fetcher_task_runner| should be an IO capable task runner able to
+  // support UrlFetcherDownloader. |background_task_runner| should be an
+  // IO capable thread able to support BackgroundDownloader.
+  static CrxDownloader* Create(
+      bool is_background_download,
+      net::URLRequestContextGetter* context_getter,
+      scoped_refptr<base::SequencedTaskRunner> url_fetcher_task_runner,
+      scoped_refptr<base::SingleThreadTaskRunner> background_task_runner);
+  virtual ~CrxDownloader();
+
+  void set_progress_callback(const ProgressCallback& progress_callback);
+
+  // Starts the download. One instance of the class handles one download only.
+  // One instance of CrxDownloader can only be started once, otherwise the
+  // behavior is undefined. The callback gets invoked if the download can't
+  // be started.
+  void StartDownloadFromUrl(const GURL& url,
+                            const DownloadCallback& download_callback);
+  void StartDownload(const std::vector<GURL>& urls,
+                     const DownloadCallback& download_callback);
+
+  const std::vector<DownloadMetrics> download_metrics() const;
+
+ protected:
+  explicit CrxDownloader(scoped_ptr<CrxDownloader> successor);
+
+  // Handles the fallback in the case of multiple urls and routing of the
+  // download to the following successor in the chain. Derived classes must call
+  // this function after each attempt at downloading the urls provided
+  // in the StartDownload function.
+  // In case of errors, |is_handled| indicates that a server side error has
+  // occured for the current url and the url should not be retried down
+  // the chain to avoid DDOS of the server. This url will be removed from the
+  // list of url and never tried again.
+  void OnDownloadComplete(bool is_handled,
+                          const Result& result,
+                          const DownloadMetrics& download_metrics);
+
+  // Calls the callback when progress is made.
+  void OnDownloadProgress(const Result& result);
+
+  // Returns the url which is currently being downloaded from.
+  GURL url() const;
+
+ private:
+  virtual void DoStartDownload(const GURL& url) = 0;
+
+  base::ThreadChecker thread_checker_;
+
+  std::vector<GURL> urls_;
+  scoped_ptr<CrxDownloader> successor_;
+  DownloadCallback download_callback_;
+  ProgressCallback progress_callback_;
+
+  std::vector<GURL>::iterator current_url_;
+
+  std::vector<DownloadMetrics> download_metrics_;
+
+  DISALLOW_COPY_AND_ASSIGN(CrxDownloader);
+};
+
+}  // namespace update_client
+
+#endif  // COMPONENTS_UPDATE_CLIENT_CRX_DOWNLOADER_H_