Add plugin stub for print preview tests

Add a plugin stub to trigger the load callback needed for print preview
tests.

BUG=717296
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2973743002
Cr-Commit-Position: refs/heads/master@{#484964}

chrome/browser/resources/print_preview/previewarea/preview_area.js

@@ -172,11 +172,6 @@ cr.define('print_preview', function() {
      */
     this.openSystemDialogButton_ = null;
 
-    /**
-     * If this is in a browser test (fake plugin).
-     * @private {boolean}
-     */
-    this.isBrowserTest_ = false;
   }
 
   /**
@@ -605,8 +600,6 @@ cr.define('print_preview', function() {
      */
     onDocumentReady_: function(event) {
       this.isDocumentReady_ = true;
-      if (this.isBrowserTest_)
-        this.isPluginReloaded_ = true;
       this.dispatchPreviewGenerationDoneIfReady_();
     },
 
@@ -675,11 +668,6 @@ cr.define('print_preview', function() {
       // being draggable.
       this.plugin_.style.pointerEvents = isDragging ? 'none' : 'auto';
     },
-
-    /** @param {boolean} isTest Whether this instance is in a browser test. */
-    setIsBrowserTest: function(isTest) {
-      this.isBrowserTest_ = isTest;
-    }
   };
 
   // Export

chrome/test/data/webui/print_preview/plugin_stub.js

+// Copyright 2017 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.
+
+cr.define('print_preview', function() {
+  /**
+   * Test version of the print preview PDF plugin
+   */
+  class PDFPluginStub {
+    /**
+     * @param {!print_preview.PreviewArea} The PreviewArea that owns this
+     *     plugin.
+     */
+    constructor(area) {
+      /**
+       * @private {?Function} The callback to run when the plugin has loaded.
+       */
+      this.loadCallback_ = null;
+
+      /** @private {!EventTracker} The plugin stub's event tracker. */
+      this.tracker_ = new EventTracker();
+
+      // Call documentLoadComplete as soon as the preview area starts the
+      // preview.
+      this.tracker_.add(
+          area,
+          print_preview.PreviewArea.EventType.PREVIEW_GENERATION_IN_PROGRESS,
+          this.documentLoadComplete.bind(this));
+    }
+
+    /**
+     * @param {!Function} callback The callback to run when the plugin has
+     *     loaded.
+     */
+    setLoadCallback(callback) {
+      this.loadCallback_ = callback;
+    }
+
+    documentLoadComplete() {
+      if (this.loadCallback_)
+        this.loadCallback_();
+    }
+
+    /**
+     * Stubbed out since some tests result in a call.
+     * @param {string} url The url to initialize the plugin to.
+     * @param {boolean} color Whether the preview should be in color.
+     * @param {!Array<number>} pages The pages to preview.
+     * @param {boolean} modifiable Whether the source document is modifiable.
+     */
+    resetPrintPreviewMode(url, color, pages, modifiable) {}
+  }
+
+  return {PDFPluginStub: PDFPluginStub};
+});

chrome/test/data/webui/print_preview/print_preview_tests.js

@@ -302,7 +302,9 @@ cr.define('print_preview_test', function() {
       print_preview.NativeLayer.setInstance(nativeLayer);
       printPreview = new print_preview.PrintPreview();
       previewArea = printPreview.getPreviewArea();
-      previewArea.setIsBrowserTest(true);
+      previewArea.plugin_ = new print_preview.PDFPluginStub(previewArea);
+      previewArea.plugin_.setLoadCallback(
+          previewArea.onPluginLoad_.bind(previewArea));
     });
 
     // Test some basic assumptions about the print preview WebUI.

chrome/test/data/webui/print_preview/print_preview_ui_browsertest.js

@@ -58,6 +58,7 @@ PrintPreviewUIBrowserTest.prototype = {
     ROOT_PATH + 'chrome/test/data/webui/test_browser_proxy.js',
     'print_preview_tests.js',
     'native_layer_stub.js',
+    'plugin_stub.js',
   ],
 };