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

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

Index: third_party/WebKit/Source/platform/network/HTTPParsers.h
diff --git a/third_party/WebKit/Source/platform/network/HTTPParsers.h b/third_party/WebKit/Source/platform/network/HTTPParsers.h
index 6c84e4aca6979e1e91c5efe5c087231321c9afa9..e2496c5380eb8d25bd64afeadd6e7c462b607b2a 100644
--- a/third_party/WebKit/Source/platform/network/HTTPParsers.h
+++ b/third_party/WebKit/Source/platform/network/HTTPParsers.h
@@ -55,14 +55,6 @@ enum ContentTypeOptionsDisposition {
   ContentTypeOptionsNosniff
 };
 
-enum XFrameOptionsDisposition {
-  XFrameOptionsInvalid,
-  XFrameOptionsDeny,
-  XFrameOptionsSameOrigin,
-  XFrameOptionsAllowAll,
-  XFrameOptionsConflict
-};
-
 // Be sure to update the behavior of
 // XSSAuditor::combineXSSProtectionHeaderAndCSP whenever you change this enum's
 // content or ordering.
@@ -132,8 +124,6 @@ parseXSSProtectionHeader(const String& header,
                          String& failureReason,
                          unsigned& failurePosition,
                          String& reportURL);
-PLATFORM_EXPORT XFrameOptionsDisposition
-parseXFrameOptionsHeader(const String&);
 PLATFORM_EXPORT CacheControlHeader
 parseCacheControlDirectives(const AtomicString& cacheControlHeader,
                             const AtomicString& pragmaHeader);