Encoding API: ignore leading/trailing whitespace in labels

Encoding API: ignore leading/trailing whitespace in labels

Per spec, matching of labels should be done after removing leading and
trailing ASCII whitespace[1]. A specific definition of whitespace is
given in the spec[2].

Test was adapted from web-platform-tests[3] but extended to cover
failure more cases and the encoder side; this will be
upstreamed/deduped eventually.

[1] https://encoding.spec.whatwg.org/#names-and-labels
[2] https://encoding.spec.whatwg.org/#ascii-whitespace
[3] https://github.com/w3c/web-platform-tests/blob/master/encoding/textdecoder-labels.html

R=jshin@chromium.org
BUG=479785
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=194676

[jsbell, 2015-04-24 17:44:41]

jshin@ - please take a look?

[jungshik at Google, 2015-04-29 20:23:28]

On 2015/04/24 17:44:41, jsbell wrote:
> jshin@ - please take a look?

Ooops. I thought I LGTM'd this, but apparently not. Sorry about that. 
LGTM

[jsbell, 2015-04-29 20:24:58]

The CQ bit was checked by jsbell@chromium.org

[commit-bot: I haz the power, 2015-04-29 20:25:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1071283004/1

[commit-bot: I haz the power, 2015-04-29 22:20:17]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=194676

[jsbell, 2015-04-29 22:31:33]

On 2015/04/29 22:20:17, I haz the power (commit-bot) wrote:
> Committed patchset #1 (id:1) as
> https://src.chromium.org/viewvc/blink?view=rev&revision=194676

Ugh, I forgot to rebase the imported/web-platform-tests version

That will probably start failing. Will rebase that shortly.

[jsbell, 2015-04-29 22:34:09]

> Ugh, I forgot to rebase the imported/web-platform-tests version
> 
> That will probably start failing. Will rebase that shortly.

Oh, false alarm - that test is skipped since the failures had unescaped control
characters that confused rietveld.