Set an explicit object type=text/plain in reload-subframe.pl.

Set an explicit object type=text/plain in reload-subframe.pl.

Otherwise, for the navigation/reload-subframe-object.html test on Linux,
the browser would return application/x-perl as the mime type, which
causes the test to fail.

I worked around this 6 years in http://crrev.com/16233 but it's time to
remove the hack.

The Chromium side hack removal is:
https://codereview.chromium.org/1131263011

BUG=488585
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=195538

[Lei Zhang, 2015-05-16 00:59:43]

thestig@chromium.org changed reviewers:
+ jochen@chromium.org

[eroman, 2015-05-16 01:11:57]

eroman@chromium.org changed reviewers:
+ eroman@chromium.org

[eroman, 2015-05-16 01:11:58]

LGTM!

[Lei Zhang, 2015-05-16 01:13:53]

The CQ bit was checked by thestig@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-05-16 01:14:12]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1139273002/1

[commit-bot: I haz the power, 2015-05-16 03:41:09]

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

[commit-bot: I haz the power, 2015-05-16 03:41:10]

Dry run: This issue passed the CQ dry run.

[jochen (gone - plz use gerrit), 2015-05-19 11:03:44]

lgtm

[Lei Zhang, 2015-05-19 17:04:53]

The CQ bit was checked by thestig@chromium.org

[commit-bot: I haz the power, 2015-05-19 17:05:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1139273002/1

[commit-bot: I haz the power, 2015-05-19 18:37:36]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=195538