Process null capabilities as a capability fetch failure.

chrome/browser/resources/print_preview/native_layer.js

Index: chrome/browser/resources/print_preview/native_layer.js
diff --git a/chrome/browser/resources/print_preview/native_layer.js b/chrome/browser/resources/print_preview/native_layer.js
index 22a94693450b9fed47d36c889a5c0af8b515e81e..034b7aa3bf3bde55ec919ad98d099d396a083efe 100644
--- a/chrome/browser/resources/print_preview/native_layer.js
+++ b/chrome/browser/resources/print_preview/native_layer.js
@@ -550,6 +550,8 @@ cr.define('print_preview', function() {
      * @private
      */
     onUpdateWithPrinterCapabilities_: function(settingsInfo) {
+      assert(settingsInfo.capabilities,
+          'Capabilities update without capabilites');
       var capsSetEvent = new Event(NativeLayer.EventType.CAPABILITIES_SET);
       capsSetEvent.settingsInfo = settingsInfo;
       this.dispatchEvent(capsSetEvent);