 this previously used a testnavigationobserver  but this no longer works for the filesystem url following mustafa s r because a top level filesystem url navigation will be blocked on the renderer side i wanted to keep this test uniformly handling both blob and filesystem urls  so i tried to use waitforloadstop which just exits immediately if a navigation has not started yet however  with blob  urls  that still did not work  because that navigation is scheduled on the renderer side  so the executescript that sets location above returns before we have received the beginnavigation from the renderer hence this ugly extra dummy executescript without it  we performed the checks below too early  and when gettextcontent below did a roundtrip to the renderer  we actually received the beginnavigation and created a speculative rfh  which caused getrenderframehostsforextension to fail  alternatively  i could wait for filesystem urls to fail with a console error  similar to what mustafa did on line does the console error approach work for both blob and filesystem urls if so  it might be better to stick with one semi awkward technique for this file than have different ones in different tests  otherwise  this seems ok given the explanatory comment no  unfortunately blobs do not output the console error given that  i will stick with this approach  separately  in light of mustafa s change  once we are certain that it sticks we might want to kill the renderer if it actually sends us a beginnavigation with a top level filesystem url  to handle the compromised renderer case  and add a separate test for that  yes  it would be a good thing to add to the cancommiturl checks  which i am currently working on in  