Bug 1417238 - hide 'open link in container' menu when there are no containers, r=jkt

Differential Revision: https://phabricator.services.mozilla.com/D37439

--HG--
extra : moz-landing-system : lando

browser/base/content/nsContextMenu.js

@@ -442,9 +442,9 @@ nsContextMenu.prototype = {
     var shouldShow =
       this.onSaveableLink || isMailtoInternal || this.onPlainTextLink;
     var isWindowPrivate = PrivateBrowsingUtils.isWindowPrivate(window);
-    var showContainers = Services.prefs.getBoolPref(
-      "privacy.userContext.enabled"
-    );
+    let showContainers =
+      Services.prefs.getBoolPref("privacy.userContext.enabled") &&
+      ContextualIdentityService.getPublicIdentities().length;
     this.showItem("context-openlink", shouldShow && !isWindowPrivate);
     this.showItem(
       "context-openlinkprivate",

browser/base/content/test/contextMenu/browser_contextmenu.js

@@ -17,7 +17,9 @@ let LOGIN_FILL_ITEMS = [
   null,
 ];
 let hasPocket = Services.prefs.getBoolPref("extensions.pocket.enabled");
-let hasContainers = Services.prefs.getBoolPref("privacy.userContext.enabled");
+let hasContainers =
+  Services.prefs.getBoolPref("privacy.userContext.enabled") &&
+  ContextualIdentityService.getPublicIdentities().length;
 
 const example_base =
   "http://example.com/browser/browser/base/content/test/contextMenu/";