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

third_party/WebKit/Source/core/dom/DocumentInit.cpp

Index: third_party/WebKit/Source/core/dom/DocumentInit.cpp
diff --git a/third_party/WebKit/Source/core/dom/DocumentInit.cpp b/third_party/WebKit/Source/core/dom/DocumentInit.cpp
index 19d9eb60be68cea26400c506b69b71865ad1288c..0ac3139e5fd37d342bb0014552ab3b297a9cbf45 100644
--- a/third_party/WebKit/Source/core/dom/DocumentInit.cpp
+++ b/third_party/WebKit/Source/core/dom/DocumentInit.cpp
@@ -96,13 +96,13 @@ SandboxFlags DocumentInit::getSandboxFlags() const {
   FrameLoader* loader = &frameForSecurityContext()->loader();
   SandboxFlags flags = loader->effectiveSandboxFlags();
 
-  // If the load was blocked by X-Frame-Options or CSP, force the Document's
-  // origin to be unique, so that the blocked document appears to be a normal
-  // cross-origin document's load per CSP spec:
-  // https://www.w3.org/TR/CSP2/#directive-frame-ancestors
+  // If the load was blocked by CSP, force the Document's origin to be unique,
+  // so that the blocked document appears to be a normal cross-origin document's
+  // load per CSP spec: https://www.w3.org/TR/CSP3/#directive-frame-ancestors.
   if (loader->documentLoader() &&
-      loader->documentLoader()->wasBlockedAfterXFrameOptionsOrCSP())
+      loader->documentLoader()->wasBlockedAfterCSP()) {
     flags |= SandboxOrigin;
+  }
 
   return flags;
 }