DevTools: [CodeMirror] Fast mark-selection addon
DevTools: [CodeMirror] Fast mark-selection addon

Pull improved mark-selection add-on from the upstream.
This fixes O(N^2) complexity of text selection.

BUG=236372

Review URL: https://chromiumcodereview.appspot.com/15072006

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@150507 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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