Use addBookmark instead of addSite for bookmarks

Fix brave#11033

We currently don't have DND under automated so no extra test coverage.

The js/dnd change is if you drag a bookmark from Chrome to Brave it was erroring with a JS error before instead of creating the bookmark.  Now it works.

This is a subset of a larger change that we needed for 0.18.x and 0.19.x
only.

Those changesets are:
582224d
48fee97

Auditors: @cezaraugusto

js/dnd.js

@@ -136,7 +136,9 @@ module.exports.prepareBookmarkDataFromCompatible = (dataTransfer) => {
   let bookmark = dndData.getDragData(dataTransfer, dragTypes.BOOKMARK)
   if (!bookmark) {
     const dragData = dndData.getDragData(dataTransfer, dragTypes.TAB)
-    windowActions.onFrameBookmark(dragData.get('tabId'))
+    if (dragData) {
+      windowActions.onFrameBookmark(dragData.get('tabId'))
+    }
   }
   return bookmark
 }