DevTools: [CodeMirror] Roll codemirror

This patch rolls codeMirror to SHA@88a03e38 (which is slightly after
v.3.15)

TBR=vsevik

Review URL: https://chromiumcodereview.appspot.com/21042008

git-svn-id: svn://svn.chromium.org/blink/trunk@155180 bbb929c8-8fbe-4397-9dbb-9b2b20218538