Fix issue in which stale downloads were added to holding space.

Previously downloads were being observed prior to download manager
initialization. When the download manager updated, these downloads
were then being added to holding space despite being stale.

Bug: 1137035
Change-Id: Icc53367f5d0d00248da2e29a2ee53a562687b22d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2464262Reviewed-by: Ahmed Mehfooz <amehfooz@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#815918}

chrome/browser/ui/ash/holding_space/holding_space_downloads_delegate.cc

@@ -91,7 +91,10 @@ void HoldingSpaceDownloadsDelegate::ManagerGoingDown(
 void HoldingSpaceDownloadsDelegate::OnDownloadCreated(
     content::DownloadManager* manager,
     download::DownloadItem* item) {
-  download_item_observer_.Add(item);
+  // Ignore `OnDownloadCreated()` events prior to `manager` initialization. For
+  // those events we bind any observers necessary in `OnManagerInitialized()`.
+  if (!is_restoring_persistence() && manager->IsManagerInitialized())
+    download_item_observer_.Add(item);
 }
 
 void HoldingSpaceDownloadsDelegate::OnDownloadUpdated(