Bug 1695264, display sync settings in fxa panel only when more than 1 device is connected r=mconley

Differential Revision: https://phabricator.services.mozilla.com/D106654

browser/base/content/browser-sync.js

@@ -111,6 +111,10 @@ this.SyncedTabsPanelList = class SyncedTabsPanelList {
       // resolving and now.
       return undefined;
     }
+    const syncPrefsButtonEl = PanelMultiView.getViewNode(
+      document,
+      "PanelUI-fxa-menu-sync-prefs-button"
+    );
     return SyncedTabs.getTabClients()
       .then(clients => {
         let noTabs = !UIState.get().syncEnabled || !clients.length;
@@ -119,6 +123,9 @@ this.SyncedTabsPanelList = class SyncedTabsPanelList {
           this.separator.hidden = noTabs;
         }
 
+        syncPrefsButtonEl.hidden =
+          !UIState.get().syncEnabled || clients.length <= 1;
+
         // The view may have been hidden while the promise was resolving.
         if (!this.tabsList) {
           return;
@@ -819,11 +826,6 @@ var gSync = {
       "PanelUI-fxa-menu-setup-sync-button"
     );
 
-    const syncPrefsButtonEl = PanelMultiView.getViewNode(
-      document,
-      "PanelUI-fxa-menu-sync-prefs-button"
-    );
-
     const syncNowButtonEl = PanelMultiView.getViewNode(
       document,
       "PanelUI-fxa-menu-syncnow-button"
@@ -861,7 +863,6 @@ var gSync = {
     syncNowButtonEl.hidden = true;
     fxaMenuAccountButtonEl.classList.remove("subviewbutton-nav");
     fxaMenuAccountButtonEl.removeAttribute("closemenu");
-    syncPrefsButtonEl.hidden = true;
     syncSetupButtonEl.removeAttribute("hidden");
 
     if (state.status === UIState.STATUS_NOT_CONFIGURED) {
@@ -909,7 +910,6 @@ var gSync = {
 
       if (state.syncEnabled) {
         syncNowButtonEl.removeAttribute("hidden");
-        syncPrefsButtonEl.removeAttribute("hidden");
         syncSetupButtonEl.hidden = true;
         document.l10n.setAttributes(
           syncNowLabel,