Leave fullscreen mode in an app window when ESC key is pressed.

chrome/common/extensions/api/_permission_features.json

 // Copyright (c) 2012 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.
 
 // See c/c/e/features/* to understand this file, in particular feature.h,
 // simple_feature.h, and base_feature_provider.h.
 
 // To add a new whitelisted ID, SHA-1 it and force it to uppercase. In Bash:
 //
 // $ echo -n "aaaabbbbccccddddeeeeffffgggghhhh" | \
@@ skipping 563 matching lines @@
     // available only to extension/platform_app types. The implementation of
     // that functionality enforces that restriction in
     // NotificationsApiFunction::IsNotificationsApiAvailable(). This is more
     // complicated than other namespaces because we are sharing the
     // notifications permission with WebKit/Blink notifications.
     "channel": "stable",
     "extension_types": [
       "extension", "legacy_packaged_app", "hosted_app", "platform_app"
     ]
   },
+  "overrideEscFullscreen": {
+    "channel": "stable",
+    "extension_types": ["platform_app"]
+  },
   "echoPrivate": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"],
     "location": "component"
   },
   "pageCapture": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
   "pointerLock": {
@@ skipping 268 matching lines @@
     // Only allowed for whitelisted extensions until all the caveats are
     // addressed. Tracked in crbug/285151.
     "channel": "stable",
     "extension_types": ["extension"],
     "location": "component",
     "whitelist": [
       "D519188F86D9ACCEE0412007B227D9936EB9676B"  // GAIA Component Extension
     ]
   }]
 }