[import] Use master document's origin to resolve CORS

[import] Use master document's origin to resolve CORS

This follows the spec change on https://www.w3.org/Bugs/Public/show_bug.cgi?id=24905
where the fetch origin is given by the master document, not the referring document.
This matches what CSP in imports is doing: Using master's CSP directive to regulate
all the imports.

In implemntation, it just set ResourceLoaderOptions::m_securityOrigin in
FetchRequest::setCrossOriginAccessControl() because HTMLImportsController
happened to pass the master' origin already.
(That was wrong but wasn't covered by the test.)

This change doesn't affect other FetchRequest client because in other callsite,
m_securityOrigin is same as one that is used when it is absent.

TEST=cors-same-origin.html
BUG=348671
R=abarth@chromium.org, dglazkov@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=168497

[Hajime Morrita, 2014-03-05 00:07:21]

PTAL?

[abarth-chromium, 2014-03-05 00:25:46]

lgtm

[Hajime Morrita, 2014-03-05 01:10:47]

The CQ bit was checked by morrita@chromium.org

[commit-bot: I haz the power, 2014-03-05 01:11:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/morrita@chromium.org/186803005/1

[commit-bot: I haz the power, 2014-03-05 16:34:31]

Change committed as 168497