Bug 1657991 - Don't bail out on some printpreview tests if there are no printers. r=jwatt

Before bug 1657164 there was always some printer on Linux and this test
ran just fine.

We don't really need a printer to test print preview, the test works
just fine.

I noticed this while auditing the "lastPrinterName" checks.

Differential Revision: https://phabricator.services.mozilla.com/D86404

layout/base/tests/chrome/printpreview_bug482976_helper.xhtml

@@ -53,20 +53,11 @@ function finish() {
   window.close();
 }
 
-function run1()
-{
-/** Test for Bug 482976 **/
-  var printService = Cc["@mozilla.org/gfx/printsettings-service;1"]
-                       .getService(Ci.nsIPrintSettingsService);
-
-  if (printService.lastUsedPrinterName != '') {
+async function run1() {
   printpreview();
   ok(gWbp.doingPrintPreview, "Should be doing print preview");
   exitprintpreview();
   ok(!gWbp.doingPrintPreview, "Should not be doing print preview anymore");
-  } else {
-    todo(false, "No printer seems installed on this machine, that is necessary for this test");
-  }
   finish();
 }
 ]]></script>

layout/base/tests/chrome/printpreview_helper.xhtml

@@ -99,15 +99,7 @@ function finish() {
 
 function runTests()
 {
-  var printService = Cc["@mozilla.org/gfx/printsettings-service;1"]
-                       .getService(Ci.nsIPrintSettingsService);
-
-  if (printService.lastUsedPrinterName != '') {
   startTest1();
-  } else {
-    todo(false, "No printer seems installed on this machine, that is necessary for this test");
-    finish();
-  }
 }
 
 function compareCanvases(options = {}) {