Allow user validated downloads to complete before Safe Browsing does

Download that are prompting the user for an Advanced Protection scan
can be kept from the chrome://downloads page. Previously, these did not
complete, since the Safe Browsing scan had not finished yet. Allow
these to complete.

Bug: 1048197
Change-Id: I774ed755fd170579027cb60165e12743f87baad2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031716
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737848}

chrome/browser/download/chrome_download_manager_delegate.cc

@@ -521,7 +521,9 @@ bool ChromeDownloadManagerDelegate::IsDownloadReadyForCompletion(
       state->CompleteDownload();
       return false;
     }
-  } else if (!state->is_complete()) {
+  } else if (!state->is_complete() &&
+             item->GetDangerType() !=
+                 download::DOWNLOAD_DANGER_TYPE_USER_VALIDATED) {
     // Don't complete the download until we have an answer.
     state->set_callback(std::move(internal_complete_callback));
     return false;