Added missing assets for selected buttons in Files.app's photo editor.

chrome/browser/resources/file_manager/css/gallery.css

Index: chrome/browser/resources/file_manager/css/gallery.css
diff --git a/chrome/browser/resources/file_manager/css/gallery.css b/chrome/browser/resources/file_manager/css/gallery.css
index 7d471a91ab3e2d3be9abbaf041d7888aa190bd21..bea91d1cef1cdf2c081ca995e768c848fcb8372e 100644
--- a/chrome/browser/resources/file_manager/css/gallery.css
+++ b/chrome/browser/resources/file_manager/css/gallery.css
@@ -666,6 +666,13 @@ body {
     url('../images/gallery/2x/icon_undo.png') 2x);
 }
 
+.gallery > .toolbar button.undo:active,
+.gallery > .toolbar button.undo[pressed] {
+  background-image: -webkit-image-set(
+    url('../images/gallery/icon_undo_selected.png') 1x,
+    url('../images/gallery/2x/icon_undo_selected.png') 2x);
+}
+
 .gallery > .toolbar button.redo {
   background-image: -webkit-image-set(
     url('../images/gallery/icon_redo.png') 1x,
@@ -673,6 +680,13 @@ body {
   position: absolute;  /* Exclude from center-packing*/
 }
 
+.gallery > .toolbar button.redo:active,
+.gallery > .toolbar button.redo[pressed] {
+  background-image: -webkit-image-set(
+    url('../images/gallery/icon_redo_selected.png') 1x,
+    url('../images/gallery/2x/icon_redo_selected.png') 2x);
+}
+
 .gallery > .toolbar button[disabled] {
   opacity: 0.5;
   pointer-events: none;