De-flake window.location shadowing layout tests.

De-flake window.location shadowing layout tests.

Use onmessage instead of the iframe onload event, since the test itself
triggers navigation. Depending on the timing, the iframe onload handler
may run more than once.

BUG=381464
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185142

[dcheng, 2014-11-11 18:57:49]

dcheng@chromium.org changed reviewers:
+ japhet@chromium.org

[dcheng, 2014-11-11 18:57:50]

Thanks for the key insight--I was looking at the test from completely the wrong
perspective.

[Nate Chapin, 2014-11-11 19:11:27]

lgtm

[dcheng, 2014-11-11 19:29:03]

The CQ bit was checked by dcheng@chromium.org

[commit-bot: I haz the power, 2014-11-11 19:29:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/713453003/1

[commit-bot: I haz the power, 2014-11-11 20:36:36]

Committed patchset #1 (id:1) as 185142