Backed out changeset ab055e5ace5e (bug 1899576) for causing bc failures on browser_all_files_referenced.js CLOSED TREE

browser/components/sidebar/sidebar-customize.css

@@ -3,9 +3,23 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 .container {
+  padding-inline: var(--space-small);
   font-size: 15px;
 }
 
+.customize-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  -moz-context-properties: fill;
+  fill: currentColor;
+  color: currentColor;
+
+  .customize-close-button::part(button) {
+    background-image: url("chrome://global/skin/icons/close-12.svg");
+  }
+}
+
 .customize-firefox-tools {
   .inputs {
     display: flex;