Make it possible to set the HTTP origin header from content

Make it possible to set the HTTP origin header from content

The goal is to eventually have an empty HTTP origin header added if needed in
content rather than in FrameFetchContext::addAdditionalRequestHeaders.

BUG=376025
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177091

[clamy, 2014-06-26 15:38:47]

@japhet, ppi: PTAL

[ppi, 2014-06-26 15:58:21]

lgtm, thanks!

[abarth-chromium, 2014-06-26 17:36:22]

lgtm

[clamy, 2014-06-27 09:34:14]

The CQ bit was checked by clamy@chromium.org

[commit-bot: I haz the power, 2014-06-27 09:34:33]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/clamy@chromium.org/352313003/1

[commit-bot: I haz the power, 2014-06-27 10:41:06]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/14047)

[commit-bot: I haz the power, 2014-06-27 11:14:41]

Change committed as 177091