Print Preview: Make generate draft mode work again.

chrome/test/data/webui/print_preview.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 GEN('#include "base/feature_list.h"');
 GEN('#include "chrome/common/chrome_features.h"');
 
 /**
  * Test fixture for print preview WebUI testing.
  * @constructor
@@ skipping 1338 matching lines @@
   // increments by 1 for each startGetPreview call it makes. It should only
   // make one such call during initialization or there will be a race; see
   // crbug.com/666595
   expectEquals(printPreview.previewArea_.previewGenerator_.inFlightRequestId_,
     -1);
   this.setInitialSettings();
   expectEquals(printPreview.previewArea_.previewGenerator_.inFlightRequestId_,
     0);
   testDone();
 });
+
+// Test the preview generator to make sure the generate draft parameter is set
+// correctly. It should be false if the only change is the page range.
+TEST_F('PrintPreviewWebUITest', 'TestGenerateDraft', function() {
+  // Use a real preview generator.
+  printPreview.previewArea_.previewGenerator_ =
+      new print_preview.PreviewGenerator(printPreview.destinationStore_,
+        printPreview.printTicketStore_, this.nativeLayer_,
+        printPreview.documentInfo_);
+
+  this.setInitialSettings();
+  this.setLocalDestinations();
+  this.setCapabilities(getCddTemplate("FooDevice"));
+
+  // The first request should set |generateDraft_| to true because there was no
+  // previous print preview draft.
+  expectEquals(
+      0,
+      printPreview.previewArea_.previewGenerator_.inFlightRequestId_);
+  expectTrue(printPreview.previewArea_.previewGenerator_.generateDraft_);

[dpapad, 2017/05/01 18:08:31]

Pasting my comment from another recent print preview CL
(https://codereview.chromium.org/2849733002#msg5).

Is there a way to avoid referring to a private variable from this test? Tests
that assert on private variables tend to test a specific implementation instead
of the observed behavior of the code they are testing.

Maybe assert that something that is observable by the user on the DOM (some
button being enabled, some message being shown etc).

+
+  // Change the page range, and |generateDraft_| should be false.
+  printPreview.printTicketStore_.pageRange.updateValue("2");
+  expectEquals(
+      1,
+      printPreview.previewArea_.previewGenerator_.inFlightRequestId_);
+  expectFalse(printPreview.previewArea_.previewGenerator_.generateDraft_);
+
+  // Change the margin type, and |generateDraft_| should be true.
+  printPreview.printTicketStore_.marginsType.updateValue(
+      print_preview.ticket_items.MarginsType.Value.NO_MARGINS);
+  expectEquals(
+      2,
+      printPreview.previewArea_.previewGenerator_.inFlightRequestId_);
+  expectTrue(printPreview.previewArea_.previewGenerator_.generateDraft_);
+
+  testDone();
+});