Introduce AncestorThrottle, which will process 'X-Frame-Options' headers.

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 63210620c9f3fb59a790033b72efd34d153183d6..a6c7900f4065da69d3d9a0444f70869201533be9 100644
--- a/content/browser/loader/navigation_resource_throttle.cc
+++ b/content/browser/loader/navigation_resource_throttle.cc
@@ -237,6 +237,10 @@ void NavigationResourceThrottle::OnUIChecksPerformed(
     controller()->CancelAndIgnore();
   } else if (result == NavigationThrottle::CANCEL) {
     controller()->Cancel();
+  } else if (result == NavigationThrottle::BLOCK_RESPONSE) {
+    // TODO(mkwst): Replace this with something more specific, as the error
+    // page for this code is meant for use with extensions.
+    controller()->CancelWithError(net::ERR_BLOCKED_BY_CLIENT);
   } else {
     controller()->Resume();
   }