Fix web_accesible_resources enforcement for Site Isolation.

content/browser/loader/navigation_resource_throttle.cc

Index: content/browser/loader/navigation_resource_throttle.cc
diff --git a/content/browser/loader/navigation_resource_throttle.cc b/content/browser/loader/navigation_resource_throttle.cc
index 3c0f5121c4c188e3b599069b6e1cd0877d8d01b7..3a91f211c3a793a366e3d69d32f92c60879de8d1 100644
--- a/content/browser/loader/navigation_resource_throttle.cc
+++ b/content/browser/loader/navigation_resource_throttle.cc
@@ -259,6 +259,8 @@ void NavigationResourceThrottle::OnUIChecksPerformed(
     controller()->CancelAndIgnore();
   } else if (result == NavigationThrottle::CANCEL) {
     controller()->Cancel();
+  } else if (result == NavigationThrottle::BLOCK_REQUEST) {
+    controller()->CancelWithError(net::ERR_BLOCKED_BY_CLIENT);
   } else {
     controller()->Resume();
   }