(Re-)introduce AncestorThrottle to handle 'X-Frame-Options'.

content/browser/frame_host/navigation_handle_impl.h

Index: content/browser/frame_host/navigation_handle_impl.h
diff --git a/content/browser/frame_host/navigation_handle_impl.h b/content/browser/frame_host/navigation_handle_impl.h
index 668ba9b08fad4dbab5c84d944d862b25d27e1abb..1790f2fc4a4eecbba5a11c9a467c61614d28d037 100644
--- a/content/browser/frame_host/navigation_handle_impl.h
+++ b/content/browser/frame_host/navigation_handle_impl.h
@@ -293,9 +293,10 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
     DEFERRING_START,
     WILL_REDIRECT_REQUEST,
     DEFERRING_REDIRECT,
-    CANCELING,
+    CANCELING_REQUEST,
     WILL_PROCESS_RESPONSE,
     DEFERRING_RESPONSE,
+    CANCELING_RESPONSE,

[clamy, 2016/12/06 17:09:43]

What is the difference between CANCELING_REQUEST & CANCELING_RESPONSE?

[arthursonzogni, 2016/12/07 16:25:02]

According to me,
* CANCELLING_REQUEST happens when the request is cancelled and no network
request has been made.
* CANCELLING_RESPONSE happens when the network request has been made and the
response has be received. The navigation is canceled at this point.

Why can't we only have one common state? I don't know, I think it could be
useful for test only.
I will merge the two for the moment. @mkwst do you objections?

     READY_TO_COMMIT,
     DID_COMMIT,
     DID_COMMIT_ERROR_PAGE,