Update error-handling for fe*Lighting and feTurbulence

Update error-handling for fe*Lighting and feTurbulence

Invalid parameters now produce transparent black rather than failing the
build step.
The new behavior matches Gecko for fe*Lighting but not for feTurbulence
(where they seem to allow negative baseFrequency values), so in the
latter case we're siding with the "Negative values are unsupported"
wording in the spec[1].

[1] https://drafts.fxtf.org/filters/#element-attrdef-feturbulence-basefrequency

BUG=533457
Committed: https://crrev.com/2cfb6d58a971b3ca3ba404ef4403394d5ccdc68f
Cr-Commit-Position: refs/heads/master@{#351817}

[fs, 2015-10-01 13:46:44]

fs@opera.com changed reviewers:
+ senorblanco@chromium.org

[fs, 2015-10-01 13:46:44]

Last spec-based error-handling change (I hope...)

[Stephen White, 2015-10-01 13:55:42]

LGTM. Thanks very much for cleaning up all these edge cases!

[fs, 2015-10-01 13:57:22]

The CQ bit was checked by fs@opera.com

[commit-bot: I haz the power, 2015-10-01 13:57:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1375793003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1375793003/1

[commit-bot: I haz the power, 2015-10-01 16:34:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-01 16:35:10]

Patchset 1 (id:??) landed as
https://crrev.com/2cfb6d58a971b3ca3ba404ef4403394d5ccdc68f
Cr-Commit-Position: refs/heads/master@{#351817}