Bug 1658103 - Fix lazy translation of tab context menu. r=dao

The tab context menu is designed to not be translated until the user
interacts with the tab strip in some way. However, the tab context menu
is now shared between the tab strip and the "all tabs" panel. So, it's
possible to open the tab context menu without interacting with the tab
strip. This results in the context menu being opened before it is
translated, so the user sees an essentially blank menu. Resolve this
by adding to the all tabs panel an extra initialization step that will
automatically translate the tab context menu.

Differential Revision: https://phabricator.services.mozilla.com/D142850

browser/base/content/tabbrowser.js

@@ -6128,18 +6128,7 @@
       });
 
       let tabContextFTLInserter = () => {
-        MozXULElement.insertFTLIfNeeded("browser/tabContextMenu.ftl");
-        // Un-lazify the l10n-ids now that the FTL file has been inserted.
-        document
-          .getElementById("tabContextMenu")
-          .querySelectorAll("[data-lazy-l10n-id]")
-          .forEach(el => {
-            el.setAttribute(
-              "data-l10n-id",
-              el.getAttribute("data-lazy-l10n-id")
-            );
-            el.removeAttribute("data-lazy-l10n-id");
-          });
+        this.translateTabContextMenu();
         this.tabContainer.removeEventListener(
           "contextmenu",
           tabContextFTLInserter,
@@ -6291,6 +6280,22 @@
       });
     },
 
+    translateTabContextMenu() {
+      if (this._tabContextMenuTranslated) {
+        return;
+      }
+      MozXULElement.insertFTLIfNeeded("browser/tabContextMenu.ftl");
+      // Un-lazify the l10n-ids now that the FTL file has been inserted.
+      document
+        .getElementById("tabContextMenu")
+        .querySelectorAll("[data-lazy-l10n-id]")
+        .forEach(el => {
+          el.setAttribute("data-l10n-id", el.getAttribute("data-lazy-l10n-id"));
+          el.removeAttribute("data-lazy-l10n-id");
+        });
+      this._tabContextMenuTranslated = true;
+    },
+
     setSuccessor(aTab, successorTab) {
       if (aTab.ownerGlobal != window) {
         throw new Error("Cannot set the successor of another window's tab");

browser/modules/TabsList.jsm

@@ -199,6 +199,7 @@ class TabsPanel extends TabsListBase {
         if (!this.listenersRegistered && event.target == this.view) {
           this.panelMultiView = this.view.panelMultiView;
           this._populate(event);
+          this.gBrowser.translateTabContextMenu();
         }
         break;
       case "command":