DownloadManager intereface refactoring to allow cleaner DownloadItem unit tests.

chrome/browser/download/download_shelf_context_menu.cc

Index: chrome/browser/download/download_shelf_context_menu.cc
diff --git a/chrome/browser/download/download_shelf_context_menu.cc b/chrome/browser/download/download_shelf_context_menu.cc
index e30ab2b00afeaa41bb1cb8a719e05ce3442656c0..43a435f812eae71b12e749d94f4622d0572cb5b7 100644
--- a/chrome/browser/download/download_shelf_context_menu.cc
+++ b/chrome/browser/download/download_shelf_context_menu.cc
@@ -81,8 +81,8 @@ void DownloadShelfContextMenu::ExecuteCommand(int command_id) {
       download_item_->OpenDownload();
       break;
     case ALWAYS_OPEN_TYPE: {
-      DownloadPrefs* prefs = DownloadPrefs::FromDownloadManager(
-          download_item_->GetDownloadManager());
+      DownloadPrefs* prefs = DownloadPrefs::FromBrowserContext(
+          download_item_->BrowserContext());
       FilePath path = download_item_->GetUserVerifiedFilePath();
       if (!IsCommandIdChecked(ALWAYS_OPEN_TYPE))
         prefs->EnableAutoOpenBasedOnExtension(path);