Revert of Upgrade insecure requests: Pipe navigational hosts down into nested documents.

Revert of Upgrade insecure requests: Pipe navigational hosts down into nested documents. (patchset #1 id:1 of https://codereview.chromium.org/978323002/)

Reason for revert:
Speculative revert to see if things stop crashing. :)

BUG=465497
Original issue's description:
> Upgrade insecure requests: Pipe navigational hosts down into nested documents.
> 
> After [1], we need to track hosts (including ancestor hosts) that have
> set the 'upgrade-insecure-requests' directive in their respective policies
> in order to correctly upgrade navigational requests to one of those
> hosts.
> 
> This patch adds a 'HashSet<unsigned>' to SecurityContext that holds the
> hashes of the hosts which have opted-into such treatment, ensures that
> the set is correctly populated when creating a Document or applying a
> policy, and uses the set to make decisions about navigational upgrades
> inside ResourceFetcher.
> 
> [1]: ttps://github.com/w3c/webappsec/commit/f947b75e9b906c53d0bd6e66ca59b60bfe0aa20e
> 
> BUG=455674
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=191421

TBR=yoav@yoav.ws
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=455674
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=191650

[Mike West, 2015-03-10 18:55:29]

Created Revert of Upgrade insecure requests: Pipe navigational hosts down into
nested documents.

[commit-bot: I haz the power, 2015-03-10 18:55:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/999473002/1

[commit-bot: I haz the power, 2015-03-10 18:56:31]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=191650

[Yoav Weiss, 2015-03-10 19:03:06]

Hmm, seems like we've let a lot of unchecked possibly nullptrs slip by :/

LGTM to revert

https://codereview.chromium.org/999473002/diff/1/Source/core/dom/SecurityCont...
File Source/core/dom/SecurityContext.h (left):

https://codereview.chromium.org/999473002/diff/1/Source/core/dom/SecurityCont...
Source/core/dom/SecurityContext.h:74: void addInsecureNavigationUpgrade(const
String& host) { m_insecureNavigationsToUpgrade.add(host.impl()->hash()); }
here we trusted host.impl() to be non-null. Are we sure that's the case? If so,
worth ASSERTing once this goes back in

https://codereview.chromium.org/999473002/diff/1/Source/core/fetch/ResourceFe...
File Source/core/fetch/ResourceFetcher.cpp (left):

https://codereview.chromium.org/999473002/diff/1/Source/core/fetch/ResourceFe...
Source/core/fetch/ResourceFetcher.cpp:899: ||
document()->insecureNavigationsToUpgrade()->contains(url.host().impl()->hash()))
Again, here we relied on the existence of
document()->insecureNavigationsToUpgrade() and impl(). Worth to check for it or
assert once this goes back in.

https://codereview.chromium.org/999473002/diff/1/Source/core/fetch/ResourceFe...
File Source/core/fetch/ResourceFetcher.cpp (right):

https://codereview.chromium.org/999473002/diff/1/Source/core/fetch/ResourceFe...
Source/core/fetch/ResourceFetcher.cpp:898: || url.host() ==
document()->securityOrigin()->host())
Should we assert for document()->securityOrigin() ?