Change getExtensionPrinters to cr.sendWithPromise

chrome/browser/resources/print_preview/data/destination_store.js

Index: chrome/browser/resources/print_preview/data/destination_store.js
diff --git a/chrome/browser/resources/print_preview/data/destination_store.js b/chrome/browser/resources/print_preview/data/destination_store.js
index 19499638cd577b7a46a0f850f0cfd48baaa9da5c..82d10a0c45fde07ae10ffa8d3e8a7cf0ab0cd56c 100644
--- a/chrome/browser/resources/print_preview/data/destination_store.js
+++ b/chrome/browser/resources/print_preview/data/destination_store.js
@@ -1110,7 +1110,11 @@ cr.define('print_preview', function() {
         clearTimeout(this.extensionSearchTimeout_);
 
       this.isExtensionDestinationSearchInProgress_ = true;
-      this.nativeLayer_.startGetExtensionDestinations();
+
+      cr.addWebUIListener('extension-printers-added',
+          this.onExtensionPrintersAdded_.bind(this));
+      this.nativeLayer_.getExtensionPrinters().then(
+          this.onExtensionPrintersDone_.bind(this));
       cr.dispatchSimpleEvent(
           this, DestinationStore.EventType.DESTINATION_SEARCH_STARTED);
       this.extensionSearchTimeout_ = setTimeout(
@@ -1381,10 +1385,6 @@ cr.define('print_preview', function() {
           nativeLayerEventTarget,
           print_preview.NativeLayer.EventType.PRIVET_CAPABILITIES_SET,
           this.onPrivetCapabilitiesSet_.bind(this));
-      this.tracker_.add(
-          nativeLayerEventTarget,
-          print_preview.NativeLayer.EventType.EXTENSION_PRINTERS_ADDED,
-          this.onExtensionPrintersAdded_.bind(this));
       this.tracker_.add(
           nativeLayerEventTarget,
           print_preview.NativeLayer.EventType.EXTENSION_CAPABILITIES_SET,
@@ -1625,18 +1625,28 @@ cr.define('print_preview', function() {
     /**
      * Called when an extension responds to a getExtensionDestinations
      * request.
-     * @param {Object} event Contains information about list of printers
-     *     reported by the extension.
-     *     {@code done} parameter is set iff this is the final list of printers
-     *     returned as part of getExtensionDestinations request.
+     * @param {Array<!{extensionId: string,

[dpapad, 2017/06/03 01:00:00]

!Array

It does not seem that the function expects a null input, otherwise the call to
map() would throw an error.

[rbpotter, 2017/06/03 01:52:39]

Done.

+     *                 extensionName: string,
+     *                 id: string,
+     *                 name: string,
+     *                 description: (string|undefined),
+     *                 provisional: (boolean|undefined)}>} printers The list
+     *     containing information about printers added by an extension.
      * @private
      */
-    onExtensionPrintersAdded_: function(event) {
-      this.insertDestinations_(event.printers.map(function(printer) {
+    onExtensionPrintersAdded_: function(printers) {
+      this.insertDestinations_(printers.map(function(printer) {

[dpapad, 2017/06/03 01:00:00]

Nit: I think this is equivalent to the shorter

this.insertDestinations_(
    printers.map(print_preview.ExtensionDestinationParser.parse));

[rbpotter, 2017/06/03 01:52:40]

Done.

         return print_preview.ExtensionDestinationParser.parse(printer);
       }));
+    },
 
-      if (event.done && this.isExtensionDestinationSearchInProgress_) {
+    /**
+     * Called when all extensions are done adding printers.
+     * @param {boolean} done Whether printers are done
+     * @private
+     */
+    onExtensionPrintersDone_: function(done) {
+      if (done && this.isExtensionDestinationSearchInProgress_) {
         clearTimeout(this.extensionSearchTimeout_);
         this.endExtensionPrinterSearch_();
       }