simple markdown cell with bash syntax fails to render

1. Create a new cell
1. Set it's mode to markdown
1. Copy and paste this:

\```bash
\\(
\```

The cell will not render properly. I have tried this on Notebook v5.2 with the Python 2.7.5 kernel on Ubuntu 16.04 with Chromium 64. And Notebook v5.3 with the Python 3 kernel on Fedora with Firefox and Chromium.

Reproduce the failure by creating a markdown cell, setting its mode to markdown, and pasting the bash-marked example in the issue. Start by examining the notebook frontend's markdown-cell rendering path; done means this example renders properly in the reported notebook and browser environments.

Written by the indexing model from the issue text.