Fix flakiness of form-submission-cancelable.html.

Fix flakiness of form-submission-cancelable.html.

- Specify action= attributes to avoid recursive loading of
  form-submission-cancelable.html.
- Sequentially submit two forms.
- The FAIL line in the updated expectation file is intentional.

BUG=353066, 196640
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201475

[tkent, 2015-08-31 08:23:52]

tkent@chromium.org changed reviewers:
+ keishi@chromium.org

[tkent, 2015-08-31 08:23:52]

Keishi, please review this.

[keishi, 2015-08-31 08:29:09]

LGTM

[tkent, 2015-08-31 08:34:44]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2015-08-31 08:34:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1323573005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1323573005/1

[commit-bot: I haz the power, 2015-08-31 08:41:50]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201475