Bug 1881107 - Remove delay opening context menu due to awaiting fetched devices r=fxview-reviewers,jsudiaman,sfoster

I've moved the call to fetch devices to occur in connectedCallback rather than holding up the context menu toggle function.
https://profiler.firefox.com/from-browser/calltree/?globalTrackOrder=80w7&hiddenGlobalTracks=1w6&hiddenLocalTracksByPid=56852-134~56853-0~56859-0~56860-0~56858-0~56861-0~56857-0~56856-0&thread=c&v=10

Differential Revision: https://phabricator.services.mozilla.com/D205390

browser/components/firefoxview/opentabs.mjs

@@ -38,6 +38,9 @@ ChromeUtils.defineLazyGetter(lazy, "fxAccounts", () => {
   ).getFxAccountsSingleton();
 });
 
+const TOPIC_DEVICESTATE_CHANGED = "firefox-view.devicestate.changed";
+const TOPIC_DEVICELIST_UPDATED = "fxaccounts:devicelist_updated";
+
 /**
  * A collection of open tabs grouped by window.
  *
@@ -671,6 +674,7 @@ class OpenTabsContextMenu extends MozLitElement {
   constructor() {
     super();
     this.triggerNode = null;
+    this.boundObserve = (...args) => this.observe(...args);
     this.devices = [];
   }
 
@@ -682,6 +686,28 @@ class OpenTabsContextMenu extends MozLitElement {
     return this.ownerDocument.querySelector("view-opentabs");
   }
 
+  connectedCallback() {
+    super.connectedCallback();
+    this.fetchDevicesPromise = this.fetchDevices();
+    Services.obs.addObserver(this.boundObserve, TOPIC_DEVICELIST_UPDATED);
+    Services.obs.addObserver(this.boundObserve, TOPIC_DEVICESTATE_CHANGED);
+  }
+
+  disconnectedCallback() {
+    super.disconnectedCallback();
+    Services.obs.removeObserver(this.boundObserve, TOPIC_DEVICELIST_UPDATED);
+    Services.obs.removeObserver(this.boundObserve, TOPIC_DEVICESTATE_CHANGED);
+  }
+
+  observe(_subject, topic, _data) {
+    if (
+      topic == TOPIC_DEVICELIST_UPDATED ||
+      topic == TOPIC_DEVICESTATE_CHANGED
+    ) {
+      this.fetchDevicesPromise = this.fetchDevices();
+    }
+  }
+
   async fetchDevices() {
     const currentWindow = this.ownerViewPage.getWindow();
     if (currentWindow?.gSync) {
@@ -701,7 +727,7 @@ class OpenTabsContextMenu extends MozLitElement {
       return;
     }
     this.triggerNode = triggerNode;
-    await this.fetchDevices();
+    await this.fetchDevicesPromise;
     await this.getUpdateComplete();
     this.panelList.toggle(originalEvent);
   }