DevTools: Improve console live expressions accessible name

Added option to configure code mirrors accessible name then set console
live expressions accessible name to "Live expression editor".
Before it read "Code editor" which is the same as the primary console input.

Screenshot: https://i.imgur.com/GZDwP3F.png
Bug: 963183
Change-Id: Ie3fd3206953c54df31d6abeaeca7e5f7ad0dabee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1628224
Reviewed-by: Erik Luo <[email protected]>
Reviewed-by: Joel Einbinder <[email protected]>
Commit-Queue: John Emau <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#666359}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 5635f819724970444c02fef12e0656a9872c7c0d
diff --git a/front_end/externs.js b/front_end/externs.js
index 925c138..ace7420 100644
--- a/front_end/externs.js
+++ b/front_end/externs.js
@@ -544,7 +544,7 @@
 };
 /** @type {!{cursorDiv: Element, lineSpace: Element, gutters: Element}} */
 CodeMirror.prototype.display;
-/** @type {!{mode: string, lineWrapping: boolean}} */
+/** @type {!{devtoolsAccessibleName: string, mode: string, lineWrapping: boolean}} */
 CodeMirror.prototype.options;
 /** @type {!Object} */
 CodeMirror.Pass;