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

third_party/WebKit/Source/platform/network/ResourceError.h

Index: third_party/WebKit/Source/platform/network/ResourceError.h
diff --git a/third_party/WebKit/Source/platform/network/ResourceError.h b/third_party/WebKit/Source/platform/network/ResourceError.h
index 7e0517ff09268fe83d27661ca7a257504f2555c5..7f9163651e8ac8efd433ee305de95080584fd0f7 100644
--- a/third_party/WebKit/Source/platform/network/ResourceError.h
+++ b/third_party/WebKit/Source/platform/network/ResourceError.h
@@ -27,6 +27,7 @@
 #ifndef ResourceError_h
 #define ResourceError_h
 
+#include "net/base/net_errors.h"
 #include "platform/PlatformExport.h"
 #include "wtf/Allocator.h"
 #include "wtf/text/WTFString.h"
@@ -99,6 +100,10 @@ class PLATFORM_EXPORT ResourceError final {
   }
   bool wasIgnoredByHandler() const { return m_wasIgnoredByHandler; }
 
+  bool wasBlockedByResponse() const {
+    return m_errorCode == net::ERR_BLOCKED_BY_RESPONSE;
+  }
+
   static bool compare(const ResourceError&, const ResourceError&);
 
  private: