<third_party/skia> Fix error handling in DirectWrite with tiny text.

If there is an error while trying to determine the metrics,
we need to bail instead of potentially using uninitialized data.

R=reed@google.com, mtklein@google.com

Author: bungeman@google.com

Review URL: https://codereview.chromium.org/511783003



Change-Id: I03abc22567396b7e174380e10fc0007523355473
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>