Implement SkPicture::hasText() for SkRecord backend.

Plus, some small tweaks to the existing code surrounding it.  Just proposals,
will undo whatever you don't like.

BUG=skia:
R=mtklein@google.com, tomhudson@google.com, reed@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/494683003
4 files changed