(Re)organize handling of CORS access control during resource loading.

(Re)organize handling of CORS access control during resource loading.

Common up and simplify the various pieces of code that handles CORS
access control, avoiding per resource type handling.

That is, a ResourceLoader's host will now be called upon by the loader
when it receives the initial response. The host deciding if a response
should be allowed loaded or not:

  bool ResourceLoaderHost::canAccessResource(Resource*, const KURL&);

If not, the loader cancels the loading of the resource and signals an
error. The loader host is responsible for emitting a suitable console
error message.

Switch over the 'loader' resource clients to rely on that, avoiding
custom CORS checks (and error reporting) for scripts, imports, images,
text tracks.

As the resource loader now needs to know if a load operation is CORS
enabled or not, this is now/again recorded by ResourceLoaderOptions.

R=abarth@chromium.org,japhet@chromium.org
BUG=178787
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=165877

[sof, 2014-01-26 22:50:27]

At your own leisure, please take a look.

Some changes to try to make CORS handling a bit more regular (a follow-on CL
enables CORS for <link> elements; it depending on the structural changes made
here.)

[abarth-chromium, 2014-01-27 18:00:43]

LGTM

This approach looks much better.  Thanks!

[Nate Chapin, 2014-01-27 18:08:14]

On 2014/01/27 18:00:43, abarth wrote:
> LGTM
> 
> This approach looks much better.  Thanks!

LGTM2!

[sof, 2014-01-27 18:43:47]

On 2014/01/27 18:08:14, Nate Chapin wrote:
> On 2014/01/27 18:00:43, abarth wrote:
> > LGTM
> > 
> > This approach looks much better.  Thanks!
> 
> LGTM2!

Thanks both :)

[commit-bot: I haz the power, 2014-01-27 18:44:09]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/sigbjornf@opera.com/137983010/50002

[commit-bot: I haz the power, 2014-01-27 19:58:48]

Change committed as 165877