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

components/error_page_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <grit-part>
 
   <message name="IDS_ERRORPAGE_NET_BUTTON_DETAILS" desc="Label for the button that expands the details on a net error page">
     Details
   </message>
   <message name="IDS_ERRORPAGE_NET_BUTTON_HIDE_DETAILS" desc="Label for the button that hides the details on a net error page">
     Hide details
   </message>
   <message name="IDS_ERRORPAGES_BUTTON_MORE" desc="Label for the button that expands the details on an error page">
@@ skipping 437 matching lines @@
   <message name="IDS_ERRORPAGES_DETAILS_TEMPORARY_BACKOFF" desc="The error message displayed when we temporarily stop sending requests to a server in order to avoid overloading it.">
     Requests to this URL have been temporarily throttled.
   </message>
 
   <message name="IDS_ERRORPAGES_SUMMARY_BLOCKED_BY_EXTENSION" desc="Summary in the error page when an extension blocks a request.">
     Requests to the server have been blocked by an extension.
   </message>
   <message name="IDS_ERRORPAGES_SUMMARY_BLOCKED_BY_ADMINISTRATOR" desc="Summary in the error page when an administrator policy blocks a request.">
     The person who set up this computer has chosen to block this site.
   </message>
+  <message name="IDS_ERRORPAGES_SUMMARY_BLOCKED_BY_RESPONSE" desc="Summary in the error page when the response blocks itself.">
+    The page at this URL has requested not to be displayed in this context.
+  </message>
   <message name="IDS_ERRORPAGES_DETAILS_BLOCKED_BY_EXTENSION" desc="The error message displayed when an extension blocks a request.">
     Requests to the server have been blocked by an extension.
   </message>
   <message name="IDS_ERRORPAGES_DETAILS_BLOCKED_BY_ADMINISTRATOR" desc="The error message displayed when a policy blocks a request.">
     Requests to the server have been blocked by a policy.
   </message>
   <message name="IDS_ERRORPAGES_DETAILS_BLOCKED_ENROLLMENT_CHECK_PENDING" desc="The error message displayed when the user tries to browse before the forced enrollment check has finished.">
     Browsing the Internet is disabled until the enterprise enrollment verification check has finished.
     You can still use the diagnostic tool presented here to troubleshoot issues with your connectivity.
   </message>
+  <message name="IDS_ERRORPAGES_DETAILS_BLOCKED_BY_RESPONSE" desc="Details in the error page when the response blocks itself.">
+    The server has chosen not to allow this page to be displayed in the current context by sending a
+    &lt;code&gt;X-Frame-Options&lt;/code&gt; header or a &lt;code&gt;Content-Security-Policy&lt;/code&gt;
+    header with a &lt;code&gt;frame-ancestors&lt;/code&gt; directive.
+  </message>
+
 
   <message name="IDS_ERRORPAGES_HTTP_POST_WARNING" desc="The error message displayed when the user navigates back or forward to a page which would resubmit post data. They can hit reload to send POST data again and load the page.">
     This webpage requires data that you entered earlier in order to be properly displayed. You can send this data again, but by doing so you will repeat any action this page previously performed.
   </message>
 
   <!-- Suggestions summary list messages. -->
   <message name="IDS_ERRORPAGES_SUGGESTION_LIST_HEADER" desc="Message that prefixes a list of suggestions to try when encountering a network error.">
     Try:
   </message>
   <message name="IDS_ERRORPAGES_SUGGESTION_CHECK_CONNECTION_SUMMARY" desc="The message displayed in a list of suggestions following a network error, suggesting the user should try checking their connnection. The suggestions list is prefixed with 'Try:'.">
@@ skipping 86 matching lines @@
     </message>
     <message name="IDS_ERRORPAGES_DETAILS_UNSAFE_PORT" desc="Details error message to tell user that the requested port is blocked as unsafe [Length: 20em]">
       Unsafe port blocked.
     </message>
     <message name="IDS_ERRORPAGES_SUMMARY_NOT_AVAILABLE_NO_EMPHASIS" desc="Summary in the error page when we can't connect to a site. [iOS only]">
       The webpage at <ph name="SITE">$1<ex>google.xom</ex></ph> might be temporarily down or it may have moved permanently to a new web address.
     </message>
   </if>
 
 </grit-part>