DevTools: [CodeMirror] roll CodeMirror to version @e20d175

This patch rolls CodeMirror and all of its modes.
This roll also adds "rebeccapurple" support to devtools code
highlighter.

Instructions for CodeMirror rolling could be found here:
https://sites.google.com/a/chromium.org/devtools-codemirror-rolling/

R=apavlov@chromium.org
TBR=apavlov, pfeldman

Review URL: https://codereview.chromium.org/354833004

git-svn-id: svn://svn.chromium.org/blink/trunk@176976 bbb929c8-8fbe-4397-9dbb-9b2b20218538