Revert "Issue #1124: [Basilisk] Remove Dev Edition theme."

This reverts commit bd9bb12027.

application/basilisk/themes/shared/devedition/urlbar-history-dropmarker.svg

@@ -0,0 +1,22 @@
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="33" height="14" viewBox="0 0 33 14">
+  <defs>
+    <polygon points="0,0 5.5,7 11,0" id="dropmarker-shape"/>
+  </defs>
+  <style>
+    use {
+      fill: #b6babf;
+    }
+    .hover {
+      fill: #61bdeb;
+    }
+    .active {
+      fill: #39ace6;
+    }
+  </style>
+  <use xlink:href="#dropmarker-shape" style="transform: translate(0, 4px)"/>
+  <use xlink:href="#dropmarker-shape" style="transform: translate(11px, 4px)" class="hover"/>
+  <use xlink:href="#dropmarker-shape" style="transform: translate(22px, 4px)" class="active"/>
+</svg>