Fix accessibility issues in AudioPlayer and VideoPlayer.

ui/file_manager/file_manager/manifest.json

 {
   // chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/
   "key": "MIGdMA0GCSqGSIb3DQEBAQUAA4GLADCBhwKBgQDlhpGghtnNJ7pluQN0RDwbUxwwi99oM35ZEaFYvxPLrf0fIEC18cfDdJi6u4aJ+UoSpgzK731L0P/k4LvK2Rz9kVKOy0+IvuRrWkT7lbrLfA1UEBh02OA1AAshjmyRg4IxCqgl8ia8XWq6HKegS1y1KXZYGgb4qp7Bh9VC4cIzswIBIw==",
   "manifest_version": 2,
   "name": "Files",
   "version": "3.0",
   "description": "File Manager",
   "incognito" : "split",
   "icons": {
     "16": "common/images/icon16.png",
@@ skipping 140 matching lines @@
     "background/js/volume_manager.js",
     "common/js/async_util.js",
     "common/js/error_util.js",
     "common/js/file_type.js",
     "common/js/metrics_base.js",
     "common/js/metrics_events.js",
     "common/js/metrics.js",
     "common/js/path_util.js",
     "common/js/util.js",
     "common/js/volume_manager_common.js",
+    "foreground/elements/files_icon_button.html",
+    "foreground/elements/files_icon_button.js",
     "foreground/elements/files_ripple.html",
     "foreground/elements/files_ripple.js",
     "foreground/elements/files_toast.html",
     "foreground/elements/files_toast.js",
     "foreground/elements/files_toggle_ripple.html",
     "foreground/elements/files_toggle_ripple.js",
     "foreground/elements/files_tooltip.html",
     "foreground/elements/files_tooltip.js",
     "foreground/js/metadata/byte_reader.js",
     "foreground/js/metadata/exif_parser.js",
@@ skipping 43 matching lines @@
         "background/js/test_util_base.js",
         "background/js/test_util.js",
         "background/js/volume_manager.js",
         "background/js/background.js"
       ]
     },
     // chrome-extension://pmfjbimdmchhbnneeidfognadeopoehp is the image loader extension.
     "content_security_policy": "default-src 'none'; script-src 'self' blob: filesystem: chrome://resources chrome-extension://pmfjbimdmchhbnneeidfognadeopoehp chrome-extension://fbjakikfhfdajcamjleinfciajelkpek; style-src 'self' blob: filesystem: 'unsafe-inline' chrome://resources chrome-extension://fbjakikfhfdajcamjleinfciajelkpek; frame-src 'self' blob: filesystem: about:; img-src 'self' blob: filesystem: chrome://resources chrome://theme data: https://docs.google.com https://*.googleusercontent.com chrome://extension-icon; media-src 'self' blob: filesystem: https://*.googleusercontent.com; connect-src https://drive.google.com https://www.google-analytics.com chrome://resources; object-src 'self' blob: filesystem:; font-src chrome://resources;"
   }
 }