Fix wrong types sent to removeWebUIListener in os_printing_page

removeWebUIListener expects a WebUIListener argument, but strings
were being passed.

This CL
1. Adds variables to keep track of created WebUIListener types
so they can be removed with removeWebUIListener in
cups_printers_entry_manager.js

2. Uses addWebUIListener from WebUIListenerBehavior for automatic
WebUIListener removal in cups_printers.js

Change-Id: I86da8dda6bf03e3ce83c38a3e63825ff4335f1f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2350335
Commit-Queue: Claude van der Merwe <cvandermerwe@google.com>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Jimmy Gong <jimmyxgong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797461}

chrome/browser/resources/settings/chromeos/os_printing_page/BUILD.gn

@@ -15,6 +15,7 @@ js_type_check("closure_compile") {
     ":cups_printer_dialog_util",
     ":cups_printers",
     ":cups_printers_browser_proxy",
+    ":cups_printers_entry_manager",
     ":cups_settings_add_printer_dialog",
     ":os_printing_page",
   ]

chrome/browser/resources/settings/chromeos/os_printing_page/cups_printers.js

@@ -33,6 +33,12 @@ Polymer({
       notify: true,
     },
 
+    /** @private {?WebUIListener} */
+    onPrintersChangedListener_: {
+      type: Object,
+      value: null,
+    },
+
     searchTerm: {
       type: String,
     },
@@ -128,13 +134,17 @@ Polymer({
    */
   currentRouteChanged(route) {
     if (route != settings.routes.CUPS_PRINTERS) {
-      cr.removeWebUIListener('on-printers-changed');
+      if (this.onPrintersChangedListener_) {
+        cr.removeWebUIListener(
+            /** @type {WebUIListener} */ (this.onPrintersChangedListener_));
+        this.onPrintersChangedListener_ = null;
+      }
       this.entryManager_.removeWebUIListeners();
       return;
     }
 
     this.entryManager_.addWebUIListeners();
-    cr.addWebUIListener(
+    this.onPrintersChangedListener_ = cr.addWebUIListener(
         'on-printers-changed', this.onPrintersChanged_.bind(this));
     this.updateCupsPrintersList_();
   },

chrome/browser/resources/settings/chromeos/os_printing_page/cups_printers_entry_manager.js

@@ -41,22 +41,29 @@ cr.define('settings.printing', function() {
       /** @type {!Array<!PrinterListEntry>} */
       this.printServerPrinters = [];
 
-      /** @type {!Array<PrintersListCallback>} */
+      /** @private {!Array<PrintersListCallback>} */
       this.onNearbyPrintersChangedListeners_ = [];
+
+      /** @private {?WebUIListener} */
+      this.onNearbyPrintersChangedListener_ = null;
     }
 
     addWebUIListeners() {
       // TODO(1005905): Add on-printers-changed listener here once legacy code
       // is removed.
-      cr.addWebUIListener(
+      this.onNearbyPrintersChangedListener_ = cr.addWebUIListener(
           'on-nearby-printers-changed', this.setNearbyPrintersList.bind(this));
+
       settings.CupsPrintersBrowserProxyImpl.getInstance()
           .startDiscoveringPrinters();
     }
 
     removeWebUIListeners() {
-      cr.removeWebUIListener('on-nearby-printers-changed');
-      cr.removeWebUIListener('on-print-server-added');
+      if (this.onNearbyPrintersChangedListener_) {
+        cr.removeWebUIListener(/** @type {WebUIListener} */ (
+            this.onNearbyPrintersChangedListener_));
+        this.onNearbyPrintersChangedListener_ = null;
+      }
     }
 
     /** @return {!Array<!PrinterListEntry>} */