[TextBlob] Remove drawSimpleText blob path.

We are converting to, caching and drawing text blobs at a higher level
(TextPainter), so we can drop this initial/low-level blob code path.

R=jbroman@chormium.org,eae@chromium.org

Review URL: https://codereview.chromium.org/619853006

git-svn-id: svn://svn.chromium.org/blink/trunk@183134 bbb929c8-8fbe-4397-9dbb-9b2b20218538