Fix i18nTemplate.process() for DocumentFragments.

Fix i18nTemplate.process() for DocumentFragments.

Also simplify process() by using ::shadow, which isn't a combinator
(and therefore includes top-level elements).

R=jlklein@chromium.org
BUG=425626
Committed: https://crrev.com/fb05964faf913e285cca82d1500de978dafc9e04
Cr-Commit-Position: refs/heads/master@{#339372}

[Dan Beam, 2015-07-17 01:43:03]

Patchset #1 (id:1) has been deleted

[Dan Beam, 2015-07-17 03:00:37]

Patchset #2 (id:30001) has been deleted

[Dan Beam, 2015-07-17 03:00:44]

Patchset #1 (id:10003) has been deleted

[Jeremy Klein, 2015-07-17 17:21:05]

Have you tested this with multiple layers of shadow boundaries? ::shadow only
pierces a single layer deep.

[Jeremy Klein, 2015-07-17 20:44:57]

lgtm
verified offline

[Dan Beam, 2015-07-17 21:33:10]

Patchset #2 (id:70001) has been deleted

[Dan Beam, 2015-07-17 21:35:41]

Patchset #2 (id:90001) has been deleted

[Dan Beam, 2015-07-17 21:36:52]

The CQ bit was checked by dbeam@chromium.org

[Dan Beam, 2015-07-17 21:36:52]

The patchset sent to the CQ was uploaded after l-g-t-m from jlklein@chromium.org
Link to the patchset: https://codereview.chromium.org/1233883005/#ps110001
(title: "stronger typing")

[commit-bot: I haz the power, 2015-07-17 21:37:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1233883005/110001

[commit-bot: I haz the power, 2015-07-18 00:04:36]

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

[commit-bot: I haz the power, 2015-07-18 00:04:37]

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

[Dan Beam, 2015-07-18 00:07:43]

The CQ bit was checked by dbeam@chromium.org

[commit-bot: I haz the power, 2015-07-18 00:07:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1233883005/110001

[commit-bot: I haz the power, 2015-07-18 01:21:33]

Committed patchset #2 (id:110001)

[commit-bot: I haz the power, 2015-07-18 01:23:01]

Patchset 2 (id:??) landed as
https://crrev.com/fb05964faf913e285cca82d1500de978dafc9e04
Cr-Commit-Position: refs/heads/master@{#339372}