[TextBlob] Recompute blob bounds when empty.

[TextBlob] Recompute blob bounds when empty.

Blob bounds should never be empty, but we sometimes receive empty bounds
for glyphs with logical width == 0. In this case, let Skia re-compute
the correct bounds.

(This is a stop-gap fix for http://crbug.com/445527. For a long term fix
we need to investigate either a) using glyph overflow bounds instead of
logical bounds or b) always defer bounds computation to Skia)

BUG=445527
R=jbroman@chromium.org,eae@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=188099

[jbroman, 2015-01-08 23:38:19]

lgtm since it's temporary

[eae, 2015-01-09 00:28:22]

LGTM

[eae, 2015-01-09 00:28:25]

The CQ bit was checked by eae@chromium.org

[commit-bot: I haz the power, 2015-01-09 00:29:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/820093005/1

[commit-bot: I haz the power, 2015-01-09 02:18:15]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=188099