Fix handling of large xml documents

Fix handling of large xml documents

libxml 2.9.0 (we updated from 2.7.x to 2.9.2 for M45) added a
default-on abort on > 10,000,000 byte documents which is a bit
arbitrary and is causing problems for users. The _HUGE option
makes it not do this. My assumption is that this is reasonable
behaviour security-wise as: 1) we were doing it this way until
recently; and 2) it shouldn't be any worse in the renderer than
just doing `for (;;) x+='y';`

(There's a big trivial xml file in
LayoutTests/http/tests/xmlhttprequest/resources/big.xml
that goes with the test, but git cl upload won't upload it. I
guess I'll dcommit just that file first?)

R=dominicc@chromium.org
BUG=528078, 463958
TEST=LayoutTests/http/tests/xmlhttprequest/xmlhttprequest-big-document.html

Committed: https://crrev.com/c73ad41c39b80ca368902a7f58fc9763b8661728
git-svn-id: svn://svn.chromium.org/blink/trunk@201992 bbb929c8-8fbe-4397-9dbb-9b2b20218538

[dominicc (has gone to gerrit), 2015-09-07 04:35:58]

The CQ bit was checked by dominicc@chromium.org

[dominicc (has gone to gerrit), 2015-09-07 04:35:58]

lgtm

[commit-bot: I haz the power, 2015-09-07 04:36:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1316673007/10002
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1316673007/10002

[commit-bot: I haz the power, 2015-09-07 05:38:06]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-09-07 05:38:07]

Try jobs failed on following builders:
  win_chromium_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[scottmg, 2015-09-08 17:03:27]

I landed the resource xml (here https://codereview.chromium.org/1328093005 but
it's useless), so going to cq this again now.

[scottmg, 2015-09-08 17:03:30]

The CQ bit was checked by scottmg@chromium.org

[commit-bot: I haz the power, 2015-09-08 17:03:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1316673007/10002
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1316673007/10002

[commit-bot: I haz the power, 2015-09-08 17:48:38]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-09-08 17:48:39]

Try jobs failed on following builders:
  linux_chromium_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[scottmg, 2015-09-09 17:44:32]

The CQ bit was checked by scottmg@chromium.org

[scottmg, 2015-09-09 17:44:32]

The patchset sent to the CQ was uploaded after l-g-t-m from
dominicc@chromium.org
Link to the patchset: https://codereview.chromium.org/1316673007/#ps20001
(title: "rebase")

[commit-bot: I haz the power, 2015-09-09 17:44:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1316673007/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1316673007/20001

[commit-bot: I haz the power, 2015-09-09 18:55:47]

Committed patchset #4 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201992

[commit-bot: I haz the power, 2015-09-23 12:01:41]

Patchset 4 (id:??) landed as
https://crrev.com/c73ad41c39b80ca368902a7f58fc9763b8661728