Remove the allow-displaying-mixed-content setting from Blink.

third_party/WebKit/LayoutTests/http/tests/fetch/resources/init.js

 if (window.testRunner) {
   // In Chromium we need to change the setting to disallow displaying
   // insecure contents.
 
   // By default, LayoutTest content_shell returns allowed for
   // "Should fetching request be blocked as mixed content?" at Step 5:
   // https://w3c.github.io/webappsec/specs/mixedcontent/#should-block-fetch
   // > If the user agent has been instructed to allow mixed content
   // Turning the switch below to false makes this condition above false, and
   // make content_shell to run into Step 7 to test mixed content blocking.
   testRunner.overridePreference('WebKitAllowRunningInsecureContent', false);
-  //FIXME: to be removed.
-  //testRunner.overridePreference('WebKitAllowDisplayingInsecureContent', true);
 
   // Accept all cookies.
   testRunner.setBlockThirdPartyCookies(false);
 }
 
 // How tests starts:
 // 1. http://127.0.0.1:8000/.../X.html is loaded.
 // 2. init(): Do initialization.
 //    In thorough/* tests
 //    (see init() in thorough-util.js):
@@ skipping 17 matching lines @@
         } else {
           // Step 3a. For non-base-https tests, start tests here.
           start(t);
         }
       });
 } else {
   // Step 4b. Already redirected to the HTTPS page.
   // Start tests for base-https tests here.
   start(t);
 }