Check if temp file was created before OnPageDone called

Check if temp file was created before OnPageDone called

Broken utility process may send PageDone message before
browser asked for the page. In this case emf is not allocated yet
and browser will crash later on playback.

Renamed emf() to TakeEmf() to highlight changed ownership.

BUG=none

Committed: https://crrev.com/5c796832c90f68b332b0586f9e21959d1a4915f1
Cr-Commit-Position: refs/heads/master@{#329207}

[Vitaly Buka (NO REVIEWS), 2015-05-11 17:41:02]

vitalybuka@chromium.org changed reviewers:
+ alekseys@chromium.org, avakulenko@chromium.org

[Aleksey Shlyapnikov, 2015-05-11 18:11:02]

lgtm

[Vitaly Buka (NO REVIEWS), 2015-05-11 18:13:14]

The CQ bit was checked by vitalybuka@chromium.org

[commit-bot: I haz the power, 2015-05-11 18:17:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1132393002/20001

[commit-bot: I haz the power, 2015-05-11 18:46:38]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-11 18:48:04]

Patchset 2 (id:??) landed as
https://crrev.com/5c796832c90f68b332b0586f9e21959d1a4915f1
Cr-Commit-Position: refs/heads/master@{#329207}