Bug 1482950 - Use the correct 3rdparty check in tracking annotations. r=dimi,Ehsan,mayhemer!,ehsan!

The mIsTrackingResource flag on nsIHttpChannel was split into two separate
flags depending on whether or not the resource is third-party. The correct
flag will be set by the channel classifier. Similarly, a new function was
introduced, GetIsThirdPartyTrackingResource(), for those consumers (like TP)
who only care about third-party trackers.

The existing function, GetIsTracking(), will continue to look at both
first-party and third-party trackers (the behavior since first party
tracking was added to annotations in bug 1476324).

The OverrideTrackingResource() function now allows nsHTMLDocument to
override both mIsFirstPartyTrackingResource and
mIsThirdPartyTrackingResource, but since this function is a little dangerous
and only has a single user, I added an assert to make future callers think
twice about using it to opt out of tracking annotations.

Currently, only the default storage restrictions need to look at first-party
trackers so every other consumer has been moved to
mIsThirdPartyTrackingResource or GetIsThirdPartyTrackingResource().

This effectively reverts the third-party checks added in bug 1476715 and
replaces them with the more complicated check that was added in bug 1108017.
It follows the approach that Ehsan initially suggested in bug 1476715. It
also reverts the changes in the expected values of the tracking annotation
test since these were, in hindsight, a warning about this regression.

Depends on D3722

Differential Revision: https://phabricator.services.mozilla.com/D3723

dom/html/nsHTMLDocument.cpp

@@ -1081,7 +1081,7 @@ nsHTMLDocument::CreateDummyChannelForCookies(nsIURI* aCodebaseURI)
       MOZ_ASSERT(httpChannel, "How come we're coming from an HTTP doc but "
                               "we don't have an HTTP channel here?");
       if (httpChannel) {
-        httpChannel->OverrideTrackingResource(isTracking);
+        httpChannel->OverrideTrackingFlagsForDocumentCookieAccessor(docHTTPChannel);
       }
     }
   }