Re-enable referrers and fix fatal error

Stale referrer information was being used because when a pending entry
existed, but its referrer was blank, it would wrongly use the active entry.

Fix brave/brave-browser#197

Auditors: @bridiver

components/brave_shields/browser/brave_shields_util.cc

@@ -115,8 +115,6 @@ bool ShouldSetReferrer(bool allow_referrers, bool shields_up,
     const GURL& original_referrer, const GURL& tab_origin,
     const GURL& target_url, const GURL& new_referrer_url,
     blink::WebReferrerPolicy policy, Referrer *output_referrer) {
-  return false;
-  /*
   if (!output_referrer ||
       allow_referrers ||
       !shields_up ||
@@ -131,7 +129,6 @@ bool ShouldSetReferrer(bool allow_referrers, bool shields_up,
   *output_referrer = Referrer::SanitizeForRequest(target_url,
       Referrer(new_referrer_url, policy));
   return true;
-  */
 }
 
 }  // namespace brave_shields

patches/content-browser-frame_host-navigation_request.cc.patch

@@ -1,20 +1,24 @@
 diff --git a/content/browser/frame_host/navigation_request.cc b/content/browser/frame_host/navigation_request.cc
-index cc193622958b95baf7ae5b409c8c9e8df054a0ed..fc71a6067aeb261b91421a3d4349c8891ea7df1e 100644
+index cc193622958b95baf7ae5b409c8c9e8df054a0ed..2b6bb2120c494cd04c01afb619cf186a31b9dbee 100644
 --- a/content/browser/frame_host/navigation_request.cc
 +++ b/content/browser/frame_host/navigation_request.cc
-@@ -1362,6 +1362,18 @@ void NavigationRequest::CommitNavigation() {
+@@ -1362,6 +1362,22 @@ void NavigationRequest::CommitNavigation() {
           render_frame_host ==
               frame_tree_node_->render_manager()->speculative_frame_host());
 
 +  auto* pending_entry =
 +    frame_tree_node_->navigator()->GetController()->GetPendingEntry();
-+  if (pending_entry && !pending_entry->GetReferrer().url.is_empty()) {
-+    common_params_.referrer = pending_entry->GetReferrer();
++  if (pending_entry) {
++    if (!pending_entry->GetReferrer().url.is_empty()) {
++      common_params_.referrer = pending_entry->GetReferrer();
++    }
 +  } else {
 +    auto* last_committed_entry =
 +      frame_tree_node_->navigator()->GetController()->GetLastCommittedEntry();
-+    if (last_committed_entry && !last_committed_entry->GetReferrer().url.is_empty()) {
-+      common_params_.referrer = last_committed_entry->GetReferrer();
++    if (last_committed_entry) {
++      if (!last_committed_entry->GetReferrer().url.is_empty()) {
++        common_params_.referrer = last_committed_entry->GetReferrer();
++      }
 +    }
 +  }
 +