[NaCl SDK AppEngine] Fix PNaCl demos after html5 onpopstate change.

[NaCl SDK AppEngine] Fix PNaCl demos after html5 onpopstate change.

window.onpopstate used to be called with a null state when a page was
loaded for the first time. This was a bug, and inconsistent with other
browsers, but we relied on it in the PNaCl demo page.

Without it, direct links to a demo page were not working properly. Even
after fixing this, I ran into issues with history when creating/destroying
a new iframe element whenever the page switched. Using
iframe.contentDocument.location.replace seems to have fixed these issues.

No trybots because this only affects the AppEngine demo page.

BUG=none
R=sbc@chromium.org
NOTRY=true

Committed: https://crrev.com/4d1fef58494b664d1ba514c52fd0606498d67a5f
Cr-Commit-Position: refs/heads/master@{#296526}

[binji, 2014-09-24 21:23:36]

ping

[Sam Clegg, 2014-09-24 21:27:50]

lgtm

[binji, 2014-09-24 21:34:19]

Committed patchset #1 (id:1) manually as 4d1fef5 (presubmit successful).

[commit-bot: I haz the power, 2014-09-24 21:34:20]

Patchset 1 (id:??) landed as
https://crrev.com/4d1fef58494b664d1ba514c52fd0606498d67a5f
Cr-Commit-Position: refs/heads/master@{#296526}