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diff --git a/chromium/content/browser/frame_host/webui_navigation_throttle.h b/chromium/content/browser/frame_host/webui_navigation_throttle.h
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+// Copyright 2018 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_WEBUI_NAVIGATION_THROTTLE_H_
+#define CONTENT_BROWSER_FRAME_HOST_WEBUI_NAVIGATION_THROTTLE_H_
+
+#include "content/public/browser/navigation_throttle.h"
+
+namespace content {
+
+// This NavigationThrottle class is used to check for subframe navigations to
+// web content in WebUI processes and/or chrome:// documents. When the
+// parent frame is at a chrome:// URL or is in a process with WebUI
+// bindings, subframes are only allowed to navigate to chrome:// URLs.
+// Note: There are WebUI documents that live on non-chrome: schemes and do
+// not have WebUI bindings. Those are not covered by this restriction.
+//
+// This is an important security property to uphold, because by default
+// WebUI documents have high privileges and if malicious web content is
+// loaded in their process, it can be used as an easy step towards a sandbox
+// escape.
+//
+// Note: Navigations in the main frame are allowed, as those will result in a
+// process change with BrowsingInstance change and drop of privileges.
+// Subframes are resticted because they must be in the same BrowsingInstance
+// and would have the ability to communicate with the parent document.
+class WebUINavigationThrottle : public NavigationThrottle {
+ public:
+  static std::unique_ptr<NavigationThrottle> CreateThrottleForNavigation(
+      NavigationHandle* navigation_handle);
+
+  explicit WebUINavigationThrottle(NavigationHandle* navigation_handle);
+  ~WebUINavigationThrottle() override;
+
+  // NavigationThrottle methods
+  ThrottleCheckResult WillStartRequest() override;
+  const char* GetNameForLogging() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(WebUINavigationThrottle);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_FRAME_HOST_WEBUI_NAVIGATION_THROTTLE_H_