Dark Mode: make downloads item separator border fully opaque

Request from Namrata.

R=aee@chromium.org
BUG=883049

Change-Id: I0421fa21a9d9cb3b7b543b131437142f8dbb176f
Reviewed-on: https://chromium-review.googlesource.com/c/1409921
Reviewed-by: Esmael El-Moslimany <aee@chromium.org>
Commit-Queue: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622738}
diff --git a/chrome/browser/resources/md_downloads/item.html b/chrome/browser/resources/md_downloads/item.html
index 8da6b30..0b57369 100644
--- a/chrome/browser/resources/md_downloads/item.html
+++ b/chrome/browser/resources/md_downloads/item.html
@@ -74,7 +74,7 @@
 
       :host-context([dark]) #content:not(.is-active) {
         background: none;  /* override */
-        border-color: rgba(var(--google-grey-800-rgb), .8);
+        border-color: var(--google-grey-800);
       }
 
       #details {