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

content/browser/frame_host/ancestor_throttle.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_BROWSER_FRAME_HOST_ANCESTOR_THROTTLE_H_
+#define CONTENT_BROWSER_FRAME_HOST_ANCESTOR_THROTTLE_H_
+
+#include <memory>
+#include <string>
+
+#include "base/gtest_prod_util.h"
+#include "base/macros.h"
+#include "content/public/browser/navigation_throttle.h"
+
+namespace net {
+class HttpResponseHeaders;
+}
+
+namespace content {
+class NavigationHandle;
+
+// An AncestorThrottle is responsible for enforcing a resource's embedding
+// rules, and blocking requests which violate them.
+class CONTENT_EXPORT AncestorThrottle : public NavigationThrottle {
+ public:
+  enum class HeaderDisposition {
+    NONE = 0,
+    DENY,
+    SAMEORIGIN,
+    ALLOWALL,
+    INVALID,
+    CONFLICT,
+    BYPASS
+  };
+
+  static std::unique_ptr<NavigationThrottle> MaybeCreateThrottleFor(
+      NavigationHandle* handle);
+
+  ~AncestorThrottle() override;
+
+  NavigationThrottle::ThrottleCheckResult WillProcessResponse() override;
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(AncestorThrottleTest, ParsingXFrameOptions);
+  FRIEND_TEST_ALL_PREFIXES(AncestorThrottleTest, ErrorsParsingXFrameOptions);
+  FRIEND_TEST_ALL_PREFIXES(AncestorThrottleTest,
+                           IgnoreWhenFrameAncestorsPresent);
+
+  explicit AncestorThrottle(NavigationHandle* handle);
+  void ParseError(const std::string& value, HeaderDisposition disposition);
+  void ConsoleError(HeaderDisposition disposition);
+
+  // Parses an 'X-Frame-Options' header. If the result is either CONFLICT
+  // or INVALID, |header_value| will be populated with the value which caused
+  // the parse error.
+  HeaderDisposition ParseHeader(const net::HttpResponseHeaders* headers,
+                                std::string* header_value);
+
+  DISALLOW_COPY_AND_ASSIGN(AncestorThrottle);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_FRAME_HOST_ANCESTOR_THROTTLE_H_