fix width bug in popup only when needed (Chrome 66-69)

popup/popup.css

@@ -8,12 +8,6 @@
   --outer-padding: 9px;
 }
 
-html {
-  /* Chrome 66-?? adds a gap equal to the scrollbar width,
-     which looks like a bug, see https://crbug.com/821143 */
-  overflow: overlay;
-}
-
 html, body {
   height: min-content;
   max-height: 600px;

popup/popup.js

@@ -1,5 +1,5 @@
 /* global configDialog hotkeys msg
-  getActiveTab FIREFOX URLS API onDOMready $ $$ prefs
+  getActiveTab CHROME FIREFOX URLS API onDOMready $ $$ prefs
   setupLivePrefs template t $create animateElement
   tryJSONparse CHROME_HAS_BORDER_BUG */
 
@@ -15,6 +15,10 @@ const ABOUT_BLANK = 'about:blank';
 const ENTRY_ID_PREFIX_RAW = 'style-';
 const ENTRY_ID_PREFIX = '#' + ENTRY_ID_PREFIX_RAW;
 
+if (CHROME >= 3345 && CHROME < 3533) { // Chrome 66-69 adds a gap, https://crbug.com/821143
+  document.head.appendChild($create('style', 'html { overflow: overlay }'));
+}
+
 toggleSideBorders();
 
 initTabUrls()