Refactor the interface for the CrxDownloader to take a callback.

chrome/browser/component_updater/url_fetcher_downloader.cc

Index: chrome/browser/component_updater/url_fetcher_downloader.cc
diff --git a/chrome/browser/component_updater/url_fetcher_downloader.cc b/chrome/browser/component_updater/url_fetcher_downloader.cc
index 4d2f0e2b490f63d3345a01046f05505979b2bb79..d2d2f3132ed4233b5faf77d42e73f2e6928c30cc 100644
--- a/chrome/browser/component_updater/url_fetcher_downloader.cc
+++ b/chrome/browser/component_updater/url_fetcher_downloader.cc
@@ -17,9 +17,8 @@ namespace component_updater {
 UrlFetcherDownloader::UrlFetcherDownloader(
     scoped_ptr<CrxDownloader> successor,
     net::URLRequestContextGetter* context_getter,
-    scoped_refptr<base::SequencedTaskRunner> task_runner,
-    const DownloadCallback& download_callback)
-    : CrxDownloader(successor.Pass(), download_callback),
+    scoped_refptr<base::SequencedTaskRunner> task_runner)
+    : CrxDownloader(successor.Pass()),
       context_getter_(context_getter),
       task_runner_(task_runner),
       downloaded_bytes_(-1),