Print Preview: Add test to ensure only 1 preview is started at init

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 1235 matching lines @@
   // appears.
   var advancedSettingsCloseButton = $('advanced-settings').
       querySelector('.close-button');
   checkElementDisplayed(advancedSettingsCloseButton, true);
   checkElementDisplayed($('advanced-settings').
       querySelector('.search-box-area'), true);
 
   this.waitForAnimationToEnd('more-settings');
 });
 
+// Test that initialization with saved destination only issues one call
+// to startPreview.
+TEST_F('PrintPreviewWebUITest', 'TestInitIssuesOneRequest', function() {
+  // Load in a bunch of recent destinations with non null capabilities.
+  var initSettings = {
+    version: 2,
+    recentDestinations: [1, 2, 3].map(function(i) {
+      return {
+        id: 'ID' + i, origin: 'local', account: '',
+        capabilities: JSON.stringify(getCddTemplate('ID' + i)), name: '',

[dpapad, 2017/01/13 21:37:41]

capabilities is JSONified twice now? I would expect that you don't need to call
JSON.stringify here at all anymore, the one at line 1270 should cover it.

[rbpotter, 2017/01/13 22:52:19]

Done.

+        extensionId: '', extensionName: ''
+      };
+    }),
+  };
+  this.initialSettings_.serializedAppStateStr_ = JSON.stringify(initSettings);
+  this.setCapabilities(getCddTemplate('ID1'));
+  this.setCapabilities(getCddTemplate('ID2'));
+  this.setCapabilities(getCddTemplate('ID3'));
+
+  var previewGenerator = mock(print_preview.PreviewGenerator);
+  printPreview.previewArea_.previewGenerator_ = previewGenerator.proxy();
+
+  // On initialization we expect 18 calls to requestPreview. requestPreview
+  // is called each time a ticket item that updates the preview changes and
+  // each time there is a DocumentInfo.CHANGE event or a CAPABILITIES_CHANGE
+  // event. So we have:
+  // - 1 call from documentInfo initialization (triggers DocumentInfo.CHANGE).
+  // - 10 calls from Ticket item updates triggered by the DocumentInfo.CHANGE.
+  // - 2 calls from HeaderFooter ticket item updates triggered by the updates
+  //   to marginsType and customMargins ticket items.
+  // - 1 call from CAPABILITIES_CHANGE event called from setting the
+  //   destination.
+  // - 4 calls from ticket item updates that are triggered by the
+  //   CAPABILITIES_CHANGE event.
+  // == 18 calls total.
+  // If more calls occur, this indicates that additional CAPABILITIES_CHANGE or
+  // DocumentInfo.CHANGE events may have been fired. This would cause multiple
+  // startPreview calls will be issued from requestPreview, which leads to
+  // a race condition: see crbug.com/666595.
+  previewGenerator.expects(exactly(18)).requestPreview();
+
+  this.setInitialSettings();
+  testDone();
+});