Remove unused copyShapeResultAndGlyphPositions method

Remove the unused copyShapeResultAndGlyphPositions method from
HarfBuzzRun.

R=pdr@chromium.org

Review URL: https://codereview.chromium.org/503443002

git-svn-id: svn://svn.chromium.org/blink/trunk@180790 bbb929c8-8fbe-4397-9dbb-9b2b20218538