Factor Chrome details out of update manifest fetching.

chrome/browser/extensions/updater/chrome_extension_downloader_factory.h

+// 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 CHROME_BROWSER_EXTENSIONS_UPDATER_CHROME_EXTENSION_DOWNLOADER_FACTORY_H_
+#define CHROME_BROWSER_EXTENSIONS_UPDATER_CHROME_EXTENSION_DOWNLOADER_FACTORY_H_
+
+#include "base/memory/scoped_ptr.h"
+
+class Profile;
+
+namespace extensions {
+class ExtensionDownloader;
+class ExtensionDownloaderDelegate;
+}
+
+namespace net {
+class URLRequestContextGetter;
+}
+
+// This provides a simple static interface for constructing an
+// ExtensionDownloader suitable for use from within Chrome.
+class ChromeExtensionDownloaderFactory {
+ public:
+  // Creates a downloader with the given request context. No profile identity
+  // is associated with this downloader.
+  static scoped_ptr<extensions::ExtensionDownloader> CreateForRequestContext(
+      net::URLRequestContextGetter* request_context,
+      extensions::ExtensionDownloaderDelegate* delegate);
+
+  // Creates a downloader for a given Profile. This downloader will be able
+  // to authenticate as the signed-in user in the event that it's asked to
+  // fetch a protected download.
+  static scoped_ptr<extensions::ExtensionDownloader> CreateForProfile(
+      Profile* profile,
+      extensions::ExtensionDownloaderDelegate* delegate);
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_UPDATER_CHROME_EXTENSION_DOWNLOADER_FACTORY_H_