MD Downloads: add first meaningful paint metrics to UMA

chrome/browser/resources/md_downloads/vulcanized.html

Index: chrome/browser/resources/md_downloads/vulcanized.html
diff --git a/chrome/browser/resources/md_downloads/vulcanized.html b/chrome/browser/resources/md_downloads/vulcanized.html
index e2c4fe97dc2757a00d35f52ded5a7aebf86207f7..8b011687fbb076992417742331f872e0ac64e090 100644
--- a/chrome/browser/resources/md_downloads/vulcanized.html
+++ b/chrome/browser/resources/md_downloads/vulcanized.html
@@ -2964,13 +2964,12 @@ paper-icon-button {
 }
 
 paper-spinner-lite {
-  --paper-spinner-color: white;
-        height: 20px;
+  ;
+        --paper-spinner-color: white;
         margin: 0 6px;
         opacity: 0;
         padding: 6px;
         position: absolute;
-        width: 20px;
 }
 
 paper-spinner-lite[active] {