Fix flakiness of fast/forms/submit-change-fragment.html.

Fix flakiness of fast/forms/submit-change-fragment.html.

The test timed out in the following case:

1. document.location.search = "?n=v" requests a navigation.
2. Before the navigation happens, onload handler runTest() is executed.
3. document.forms.f.submit() navigates to
    ".../submit-change-fragment.html?n=v#firstaction"
4. Because the original document was ".../submit-change-fragment.html",
   onhashchange handler is NOT called.
5. No one calls testRunner.notifyDone().

This CL moves "?n=v" setting code to runTest(), and do early return to avoid the
form submission without "?n=v".

BUG=521860
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200798

[tkent, 2015-08-19 04:20:59]

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

[tkent, 2015-08-19 04:21:00]

Keishi, please review this.

[keishi, 2015-08-19 04:24:33]

lgtm

[tkent, 2015-08-19 04:30:24]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2015-08-19 04:30:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1302703002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1302703002/1

[commit-bot: I haz the power, 2015-08-19 05:10:04]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200798