Bug 1718605 - Fix active mode of calendar UI during account set-up. r=mkmelin

This makes two changes:
* When a tab monitor is registered, its onTabSwitched method is now called immediately with the current tab, so that its state can match the current tab at the time of registration.
* When calendar starts up, which may be during the account set-up process, the UI is not put in the "mail" mode if the account set-up tab (or other content tab) is open. Instead the "special" mode is used, which is the right mode for content tabs.

Differential Revision: https://phabricator.services.mozilla.com/D118942

--HG--
extra : rebase_source : 0b9502893d078ecfeb3bd5462f8895f11c509a5d

calendar/base/content/calendar-chrome-startup.js

@@ -127,7 +127,14 @@ async function loadCalendarComponent() {
   filter.value = filter.value || "all";
 
   // Set up mode-switching menu items and mode[v]box elements for the initial mode.
-  changeMode();
+  // At this point no tabs have been restored, so the only reason we wouldn't be
+  // in "mail" mode is if a content tab has opened to display the account set-up.
+  let tabmail = document.getElementById("tabmail");
+  if (tabmail.currentTabInfo.mode.name == "contentTab") {
+    changeMode("special");
+  } else {
+    changeMode("mail");
+  }
 
   // Set up customizeDone handlers for our toolbars.
   let toolbox = document.getElementById("calendar-toolbox");

mail/base/content/tabmail.js

@@ -421,8 +421,9 @@
    *     used in the course of wrapping the object.
    *  The following functions should be provided on the monitor object:
    * * onTabTitleChanged(aTab): Called when the tab's title changes.
-   * * onTabSwitched(aTab, aOldTab): Called when a new tab is made active.  If
-   *     this is the first tab ever, aOldTab will be null, otherwise aOldTab
+   * * onTabSwitched(aTab, aOldTab): Called when a new tab is made active.
+   *     Also called when the monitor is registered if one or more tabs exist.
+   *     If this is the first call, aOldTab will be null, otherwise aOldTab
    *     will be the previously active tab.
    * * onTabOpened(aTab, aIsFirstTab, aWasCurrentTab): Called when a new tab is
    *     opened.  This method is invoked after the tab mode's openTab method
@@ -709,6 +710,9 @@
     registerTabMonitor(aTabMonitor) {
       if (!this.tabMonitors.includes(aTabMonitor)) {
         this.tabMonitors.push(aTabMonitor);
+        if (this.tabInfo.length) {
+          aTabMonitor.onTabSwitched(this.currentTabInfo, null);
+        }
       }
     }
 

mail/components/im/content/chat-messenger.js

@@ -249,7 +249,7 @@ var chatTabType = {
     },
     onTabSwitched(aNewTab, aOldTab) {
       // aNewTab == chat is handled earlier by showTab() below.
-      if (aOldTab.mode.name == "chat") {
+      if (aOldTab?.mode.name == "chat") {
         chatHandler._onTabDeactivated(true);
       }
     },