DevTools: [CodeMirror] roll codeMirror htmlmixed mode to @8292921e

This patch rolls htmlmixed mode to include the fix of upper
case tag names.

TBR=apavlov@chromium.org

Review URL: https://codereview.chromium.org/589053002

git-svn-id: svn://svn.chromium.org/blink/trunk@182407 bbb929c8-8fbe-4397-9dbb-9b2b20218538