Escape key should exit the fullscreen mode when playing a video.

chrome/browser/resources/file_manager/js/media/video_player.js

Index: chrome/browser/resources/file_manager/js/media/video_player.js
diff --git a/chrome/browser/resources/file_manager/js/media/video_player.js b/chrome/browser/resources/file_manager/js/media/video_player.js
index 3d7de037b2d7c1cd3d360bd5ca871a031d7140a6..31d9e212b5275c02be21f09c49b2adf268ed9e66 100644
--- a/chrome/browser/resources/file_manager/js/media/video_player.js
+++ b/chrome/browser/resources/file_manager/js/media/video_player.js
@@ -58,10 +58,17 @@ function FullWindowVideoControls(
   window.addEventListener('resize', this.updateStyle.bind(this));
 
   document.addEventListener('keydown', function(e) {
-    if (e.keyIdentifier == 'U+0020') {
+    if (e.keyIdentifier == 'U+0020') {  // Space
       this.togglePlayStateWithFeedback();
       e.preventDefault();
     }
+    if (e.keyIdentifier == 'U+001B') {  // Escape
+      chrome.fileBrowserPrivate.isFullscreen(function(enabled) {
+        if (enabled)
+          chrome.fileBrowserPrivate.toggleFullscreen();
+      });
+      e.preventDefault();
+    }
   }.bind(this));
 
   util.disableBrowserShortcutKeys(document);