Clamp 'zoom' in CSSToLengthConversionData.

Clamp 'zoom' in CSSToLengthConversionData.

It's possible to reach a state of zoom=0 with compound application of a
small zoom value. (See testcase). We should therefore handle this situation
instead of asserting.

BUG=450606
R=timloh@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=189635

[Timothy Loh, 2015-02-03 05:37:16]

On 2015/01/23 12:51:20, andersr wrote:

Sorry for the slow response; can we just clamp in wherever it gets set to
something reasonable? (Animations uses numeric_limits<float>::denorm_min(), but
honestly 1e-9 should be fine)

[andersr, 2015-02-03 12:42:21]

On 2015/02/03 05:37:16, Timothy Loh wrote:
> On 2015/01/23 12:51:20, andersr wrote:
> 
> Sorry for the slow response; can we just clamp in wherever it gets set to
> something reasonable? (Animations uses numeric_limits<float>::denorm_min(),
but
> honestly 1e-9 should be fine)

PTAL. I used numeric_limits<float>::denorm_min() for consistency with
animations.

[Timothy Loh, 2015-02-06 01:05:30]

lgtm

[andersr, 2015-02-06 09:50:28]

The CQ bit was checked by andersr@opera.com

[commit-bot: I haz the power, 2015-02-06 09:50:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/871913003/40001

[commit-bot: I haz the power, 2015-02-06 11:56:46]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=189635