Initial implementation for ListThumbnailLoader.

ui/file_manager/file_manager/foreground/js/mock_thumbnail_loader.js

Index: ui/file_manager/file_manager/foreground/js/mock_thumbnail_loader.js
diff --git a/ui/file_manager/file_manager/foreground/js/mock_thumbnail_loader.js b/ui/file_manager/file_manager/foreground/js/mock_thumbnail_loader.js
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+// Copyright 2015 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.
+
+/**
+ * Mock thumbnail loader.
+ *
+ * @param {Entry} entry An entry.
+ * @param {ThumbnailLoader.LoaderType=} opt_loaderType Loader type.
+ * @param {Object=} opt_metadata Metadata.
+ * @param {string=} opt_mediaType Media type.
+ * @param {Array<ThumbnailLoader.LoadTarget>=} opt_loadTargets Load targets.
+ * @param {number=} opt_priority Priority.
+ */
+function MockThumbnailLoader(entry, opt_loaderType, opt_metadata, opt_mediaType,
+    opt_loadTargets, opt_priority) {
+  this.testImageDataUrl_ = null;
+}
+
+/**
+ * @type {string} Data url of an image.
+ */
+MockThumbnailLoader.testImageDataUrl_ = null;
+
+/**
+ * Set data url of an image which is returned for testing.
+ *
+ * @param {string} dataUrl Data url of an image.
+ */
+MockThumbnailLoader.setTestImageDataUrl = function(dataUrl) {
+  MockThumbnailLoader.testImageDataUrl_ = dataUrl;
+};
+
+/**
+ * Load an image. (This mock implementation does not attach an image to the
+ * box).
+ *
+ * @param {Element} box Box.
+ * @param {ThumbnailLoader.FillMode} fillMode Fill mode.
+ * @param {ThumbnailLoader.OptimizationMode=} opt_optimizationMode Optimization.
+ * @param {function(Image, Object)=} opt_onSuccess Success callback.
+ * @param {function()=} opt_onError Error callback.
+ * @param {function()=} opt_onGeneric Callback which is called when generic
+ *     image is used.
+ */
+MockThumbnailLoader.prototype.load = function(
+    box, fillMode, opt_optimizationMode, opt_onSuccess, opt_onError,
+    opt_onGeneric) {
+  if (opt_onSuccess && MockThumbnailLoader.testImageDataUrl_) {
+    var image = new Image();
+    image.onload = function() {
+      opt_onSuccess(image, null);
+    };
+    image.src = MockThumbnailLoader.testImageDataUrl_;
+  }
+};