Handle errors properly in FileUtilProxy::CreateTemporary.

Handle errors properly in FileUtilProxy::CreateTemporary.

If creating the temporary file failed, don't try to open it. If we can't open
it for some reason, delete the temporary so the caller can assume strong
exception safety and not have to delete the file on error.

BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=255767

[davidben, 2014-03-03 22:42:35]

This code has exactly one caller (RedirectToFileResourceHandler) and it doesn't
handle errors either, but in the interest of not making a giant CL even more
giant, I'm splitting the base::FileUtilProxy fixes into its own CL here.

[brettw, 2014-03-07 18:12:54]

lgtm

[davidben, 2014-03-07 18:17:53]

The CQ bit was checked by davidben@chromium.org

[commit-bot: I haz the power, 2014-03-07 18:20:46]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/davidben@chromium.org/183003009/1

[commit-bot: I haz the power, 2014-03-07 20:22:26]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/davidben@chromium.org/183003009/1

[commit-bot: I haz the power, 2014-03-08 10:49:47]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/davidben@chromium.org/183003009/1

[commit-bot: I haz the power, 2014-03-08 13:04:51]

Change committed as 255767