Add ad-block browsertest for when site_for_cookies is empty

[bbondy]

I think this case:
https://github.com/brave/brave-core/pull/942/files#diff-88c7c5c4d9e052b70374fe67c125d985R39

Happens when there's an iframe and inside that iframe there's a 302 redirect that happens.

There's a bug we had before brave/brave-core#942 landed where if you load this URL:
https://www.reddit.com/r/videos/comments/a2t52m/nickelodeon_just_uploaded_a_high_quality_version/

It would 302 a call to doubleclick.net and which would lead to 200 success codes for URLs which should be blocked:
https://static.doubleclick.net/instream/ad_status.js
https://googleads.g.doubleclick.net/pagead/id?slf_rd=1

This issue is posted to add an ad-block test that will cover this case.
Revert the PR mentioned to reproduce the issue.

[bbondy]

Doing this will reproduce:

diff --git a/browser/net/url_context.cc b/browser/net/url_context.cc
index 38f9a692..79e5d790 100644
--- a/browser/net/url_context.cc
+++ b/browser/net/url_context.cc
@@ -33,8 +33,9 @@ void BraveRequestInfo::FillCTXFromRequest(const net::URLRequest* request,
                                     &ctx->render_frame_id,
                                     &ctx->render_process_id,
                                     &ctx->frame_tree_node_id);
-  if (!request->site_for_cookies().is_empty()) {
+  //if (!request->site_for_cookies().is_empty()) {
     ctx->tab_url = request->site_for_cookies();
+    /*
   } else {
     // We can not always use site_for_cookies since it can be empty in certain
     // cases. See the comments in url_request.h
@@ -43,6 +44,7 @@ void BraveRequestInfo::FillCTXFromRequest(const net::URLRequest* request,
                                      ctx->render_frame_id,
                                      ctx->frame_tree_node_id).GetOrigin();
   }
+  */
   ctx->tab_origin = ctx->tab_url.GetOrigin();
   ctx->allow_brave_shields = brave_shields::IsAllowContentSettingFromIO(
       request, ctx->tab_origin, ctx->tab_origin, CONTENT_SETTINGS_TYPE_PLUGINS,

[bbondy]

Test should fail with above patch applied and pass when it isn't applied pls.

Test can go in this file with other adblock tests:
components/brave_shields/browser/ad_block_service_browsertest.cc

[bbondy]

cc @iefremov
Turns out only an iframe needed to do an XHR to reproduce it having a blank site_for_cookies.