History WebUI: Fix regression that flipped checkboxes in RTL.

Bug: 821736
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I849ddd15a632309e09c8fec627832c41b0d39abb
Reviewed-on: https://chromium-review.googlesource.com/1014623
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551454}

chrome/browser/resources/md_history/history_item.html

@@ -71,6 +71,7 @@
         height: 40px;
         margin: 0;
         padding: 0;
+        transform: none;  /* Checkboxes shouldn't flip even in RTL. */
         width: 40px;
       }