Process null capabilities as a capability fetch failure.

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 e26fd399352ff61a1b99898def8c13e985bd0cb1..5725e03c792475aeddab3b6cc7985829bbd6fdbf 100644
--- a/chrome/browser/resources/print_preview/data/destination_store.js
+++ b/chrome/browser/resources/print_preview/data/destination_store.js
@@ -1543,6 +1543,10 @@ cr.define('print_preview', function() {
      * @private
      */
     onLocalDestinationCapabilitiesSet_: function(event) {
+      var rawCapabilities = event.settingsInfo.capabilities;
+      assert(rawCapabilities != null,

[dpapad, 2017/05/01 17:39:28]

assert(rawCapabilities);

The comment does not add any extra information that is not already conveyed with
the existence of the assert().

[skau, 2017/05/01 22:51:26]

Done.

+          'Capabilities should never be null');
+
       var destinationId = event.settingsInfo['printerId'];
       var printerName = event.settingsInfo['printerName'];
       var printerDescription = event.settingsInfo['printerDescription'];
@@ -1557,7 +1561,7 @@ cr.define('print_preview', function() {
           '');
       var destination = this.destinationMap_[key];
       var capabilities = DestinationStore.localizeCapabilities_(
-          event.settingsInfo.capabilities);
+          rawCapabilities);
       // Special case for PDF printer (until local printers capabilities are
       // reported in CDD format too).
       if (destinationId ==