Rename collectHarfBuzzRuns to createHarfBuzzRuns

Rename HarfBuzzShaper::collectHarfBuzzRuns to createHarfBuzzRuns to
better represent what the method is doing.

BUG=311372
R=leviw@chromium.org

Review URL: https://codereview.chromium.org/145973009

git-svn-id: svn://svn.chromium.org/blink/trunk@166091 bbb929c8-8fbe-4397-9dbb-9b2b20218538