Handle redirects with NULL headers in PluginURLFetcher

Handle redirects with NULL headers in PluginURLFetcher

This is a minimal fix for the crash. We should pass the response code from the
URLRequestRedirectJob down from the browser, either by faking headers or by
passing it separately along with other redirect metadata in
https://crbug.com/384609. For now, treat it as 307 as all non-test
URLRequestRedirectJobs are 307.

BUG=382849
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=278883

[davidben, 2014-06-19 23:31:35]

This is kinda hacky, but since it's a crash and branch point is soon, it may be
worth checking in a minimal fix for branch. And then fix it properly either by
pushing it all out of //net with https://crbug.com/384609 or with
https://codereview.chromium.org/335123006/ (the nuisance with the latter is that
it does slightly change how URLRequestRedirectJobs appear to extensions and
possibly other code).

[mmenke, 2014-06-20 16:29:14]

LGTM, as a temporary crash fix.

[jam, 2014-06-20 20:06:14]

lgtm

[davidben, 2014-06-20 20:07:20]

The CQ bit was checked by davidben@chromium.org

[mmenke, 2014-06-20 20:07:21]

The CQ bit was checked by mmenke@chromium.org

[commit-bot: I haz the power, 2014-06-20 20:10:09]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/davidben@chromium.org/345833002/1

[commit-bot: I haz the power, 2014-06-21 01:00:39]

Change committed as 278883