Revert of PlzNavigate: Enforce 'frame-src' CSP on the browser.

chrome/test/data/extensions/api_test/sandboxed_pages_csp/sandboxed.html

 This page should be sandboxed.
 
 <script>
 // We're not served with the extension default CSP, we can use inline script.
 
-var sendResponse = function(msg) {
-  var mainWindow = window.opener || window.top;
-  mainWindow.postMessage(msg, '*');
-};
-
-var remote_frame_loaded = false;
-window.addEventListener('securitypolicyviolation', function(e) {
-  if (remote_frame_loaded)
-    sendResponse('succeeded');
-  else
-    sendResponse('failed');
-});
-
 var loadFrameExpectResponse = function(iframe, url) {
   var identifier = performance.now();
   return new Promise(function(resolve, reject) {
     window.addEventListener('message', function(e) {
       var data = JSON.parse(e.data);
       if (data[0] == 'local frame msg' && data[1] == identifier) {
         resolve();
       } else {
         reject();
       }
     });
     iframe.onerror = reject;
     iframe.onload = function() {
       iframe.contentWindow.postMessage(
           JSON.stringify(['sandboxed frame msg', identifier]), '*');
     };
     iframe.src = url;
   });
 };
 
 var runTestAndRespond = function(localUrl, remoteUrl) {
   var iframe = document.createElement('iframe');
+  var sendResponse = function(msg) {
+    var mainWindow = window.opener || window.top;
+    mainWindow.postMessage(msg, '*');
+  };
 
   // First load local resource in |iframe|, expect the local frame to respond.
   loadFrameExpectResponse(iframe, localUrl).then(function() {
-    // Then load remote resource in |iframe|, expect the navigation to be
-    // blocked by the Content-Security-Policy.
-    // Rely on the SecurityPolicyViolationEvent to detect that the frame has
-    // been blocked.
-    remote_frame_loaded = true;
-    iframe.src = remoteUrl;
+    // Then try to load remote resource on the same iframe element. The remote
+    // resource will fail to load but we'd get an iframe.onload event and the
+    // local frame will still be there. Therefore, expect the local frame to
+    // respond again.
+    return loadFrameExpectResponse(iframe, remoteUrl);
+  }).then(function() {
+    sendResponse('succeeded');
+  }).catch(function(err) {
+    sendResponse('failed');
   });
   document.body.appendChild(iframe);
 };
 
 onmessage = function(e) {
   var command = JSON.parse(e.data);
   if (command[0] == 'load') {
     var localUrl = command[1];
     var remoteUrl = command[2];
     runTestAndRespond(localUrl, remoteUrl);
   }
 };
 
 </script>