marijnh/CodeMirror — pull request #1658 by bfrohs (2013-07-08 01:24:32+00:00)
Title: [markdown] Highlight trailing spaces that affect line breaks

For https://groups.google.com/forum/?fromgroups#!topic/codemirror/gBJlh7OdP4c

`-a` and `-b` suffixes are to work around collapsing the spaces into a single `span` (which screws up the positioning of the space placeholders).