Add support to mime types in Files app UI.

ui/file_manager/integration_tests/gallery/slide_mode.js

Index: ui/file_manager/integration_tests/gallery/slide_mode.js
diff --git a/ui/file_manager/integration_tests/gallery/slide_mode.js b/ui/file_manager/integration_tests/gallery/slide_mode.js
index 372b928ce89194909dfe5f94b115d586f74b0c0a..a83982585e803f05401fc1cf27cf40cba7c7f11f 100644
--- a/ui/file_manager/integration_tests/gallery/slide_mode.js
+++ b/ui/file_manager/integration_tests/gallery/slide_mode.js
@@ -13,7 +13,7 @@
  * @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;
@@ -25,10 +25,6 @@ function traverseSlideImages(testVolumeName, volumeType) {
   }).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');