After we enables safe browsing checks on WebView, we want to know how user got to the bad page.
On desktop chrome, we use SafeBrowsingNabigationObserver/Manager to get the reliable referrer chain.
Can these attribution logic directly work on WebView?

(1) Performance concern, especially memory impact
(2) How to attribute static html page, e.g.

  facebook app  ->  foo.com -> [static html page] --> evil.com (interstitial shown)
  
  Attribution logic should be able to work with static html page in addition to URLs.