Add support to mime types in Files app UI.

ui/file_manager/integration_tests/gallery/slide_mode.js

 // Copyright 2014 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.
 
 'use strict';
 
 /**
  * Runs a test to traverse images in the slide mode.
  *
  * @param {string} testVolumeName Test volume name passed to the addEntries
  *     function. Either 'drive' or 'local'.
  * @param {VolumeManagerCommon.VolumeType} volumeType Volume type.
  * @return {Promise} Promise to be fulfilled with on success.
  */
 function traverseSlideImages(testVolumeName, volumeType) {
-  var testEntries = [ENTRIES.desktop, ENTRIES.image2, ENTRIES.image3];
+  var testEntries = [ENTRIES.desktop, ENTRIES.image3];
   var launchedPromise = launch(
       testVolumeName, volumeType, testEntries, testEntries.slice(0, 1));
   var appId;
   return launchedPromise.then(function(args) {
     appId = args.appId;
     return gallery.waitForElement(appId, '.gallery[mode="slide"]');
   }).then(function() {
     return gallery.waitForSlideImage(appId, 800, 600, 'My Desktop Background');
   }).then(function() {
     return gallery.waitAndClickElement(appId, '.arrow.right');
   }).then(function() {
-    return gallery.waitForSlideImage(appId, 1024, 768, 'image2');
-  }).then(function() {
-    return gallery.waitAndClickElement(appId, '.arrow.right');
-  }).then(function() {
     return gallery.waitForSlideImage(appId, 640, 480, 'image3');
   }).then(function() {
     return gallery.waitAndClickElement(appId, '.arrow.right');
   }).then(function() {
     return gallery.waitForSlideImage(appId, 800, 600, 'My Desktop Background');
   });
 }
 
 /**
  * Runs a test to rename an image.
@@ skipping 95 matching lines @@
   return deleteImage('local', 'downloads');
 };
 
 /**
  * The deleteImage test for Google Drive.
  * @return {Promise} Promise to be fulfilled with on success.
  */
 testcase.deleteImageOnDrive = function() {
   return deleteImage('drive', 'drive');
 };