Quick View: Show folder icon if folder is selected.

ui/file_manager/file_manager/foreground/elements/files_quick_view.css

Index: ui/file_manager/file_manager/foreground/elements/files_quick_view.css
diff --git a/ui/file_manager/file_manager/foreground/elements/files_quick_view.css b/ui/file_manager/file_manager/foreground/elements/files_quick_view.css
index 984a58d5e6db58c0672e61470293d694aa357ef7..242da3159b66860ae5abe562dab62210aaa20a5c 100644
--- a/ui/file_manager/file_manager/foreground/elements/files_quick_view.css
+++ b/ui/file_manager/file_manager/foreground/elements/files_quick_view.css
@@ -191,27 +191,28 @@ iron-icon {
   height: 88px;
 }
 
+[generic-thumbnail=".folder"] {
+  background-image: -webkit-image-set(
+      url(../images/files/ui/quick_view/filetype_folder.png) 1x,
+      url(../images/files/ui/quick_view/2x/filetype_folder.png) 2x);
+  height: 72px;
+}
+
 [generic-thumbnail='audio'] {
-  background: -webkit-image-set(
+  background-image: -webkit-image-set(
       url(../images/files/ui/quick_view/filetype_audio.png) 1x,
-      url(../images/files/ui/quick_view/2x/filetype_audio.png) 2x)
-    center
-    no-repeat;
+      url(../images/files/ui/quick_view/2x/filetype_audio.png) 2x);
 }
 
 [generic-thumbnail='image'] {
-  background: -webkit-image-set(
+  background-image: -webkit-image-set(
       url(../images/files/ui/quick_view/filetype_image.png) 1x,
-      url(../images/files/ui/quick_view/2x/filetype_image.png) 2x)
-    center
-    no-repeat;
+      url(../images/files/ui/quick_view/2x/filetype_image.png) 2x);
 }
 
 [generic-thumbnail='video'] {
-  background: -webkit-image-set(
+  background-image: -webkit-image-set(
       url(../images/files/ui/quick_view/filetype_video.png) 1x,
-      url(../images/files/ui/quick_view/2x/filetype_video.png) 2x)
-    center
-    no-repeat;
+      url(../images/files/ui/quick_view/2x/filetype_video.png) 2x);
   height: 72px;
 }