Add DIR_METADATA files to //components/download

Generate DIR_METADATA files and remove metatada from OWNERS files for
//components/download

Bug: 1113033
Change-Id: Iafaaa6b893eeef1bf2add1033bf2b12fd39a56e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2542947Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Norman Rosas <normando@google.com>
Cr-Commit-Position: refs/heads/master@{#828323}

components/download/DIR_METADATA

+monorail {
+  component: "UI>Browser>Downloads"
+}
\ No newline at end of file

components/download/OWNERS

@@ -2,5 +2,3 @@ dtrainor@chromium.org
 qinmin@chromium.org
 shaktisahu@chromium.org
 xingliu@chromium.org
-
-# COMPONENT: UI>Browser>Downloads

components/download/quarantine/DIR_METADATA

+monorail {
+  component: "UI>Browser>Downloads"
+}
\ No newline at end of file

components/download/quarantine/OWNERS

 asanka@chromium.org
 wfh@chromium.org
-
-# COMPONENT: UI>Browser>Downloads