Bug 1497795 - add confirmation for marking all folders as read. r=mkmelin

mail/base/content/mailWindowOverlay.js

@@ -2259,6 +2259,14 @@ function MsgMarkAllRead() {
  * Go through each selected server and mark all its folders read.
  */
 function MsgMarkAllFoldersRead() {
+  const bundle = document.getElementById("bundle_messenger");
+
+  if (!Services.prompt.confirm(window,
+                               bundle.getString("confirmMarkAllFoldersReadTitle"),
+                               bundle.getString("confirmMarkAllFoldersReadMessage"))) {
+    return;
+  }
+
   const selectedFolders = gFolderTreeView.getSelectedFolders();
   const selectedServers = selectedFolders.filter(folder => folder.isServer);
 

mail/locales/en-US/chrome/messenger/messenger.properties

@@ -327,6 +327,10 @@ confirmUnsubscribeTitle=Confirm Unsubscribe
 confirmUnsubscribeText=Are you sure you want to unsubscribe from %S?
 confirmUnsubscribeManyText=Are you sure you want to unsubscribe from these newsgroups?
 restoreAllTabs=Restore All Tabs
+
+confirmMarkAllFoldersReadTitle=Mark All Folders Read
+confirmMarkAllFoldersReadMessage=Are you sure you want to mark all messages in all folders of this account as read?
+
 # LOCALIZATION NOTE(junkBarMessage): %S is brand
 junkBarMessage=%S thinks this message is Junk mail.
 junkBarButton=Not Junk