DevTools: [CodeMirror] remaster text editor messages

This patch remakes text editor errors so that they will not
move lines apart. Having popover in text editor will make it possible to add stacktraces via treeoutline for errors if we would love to.

BUG=397217

Review URL: https://codereview.chromium.org/418553006

git-svn-id: svn://svn.chromium.org/blink/trunk@179654 bbb929c8-8fbe-4397-9dbb-9b2b20218538