Add a way to cancel deferred navigations in NavigationHandle

components/navigation_interception/intercept_navigation_throttle.h

 // Copyright 2015 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 COMPONENTS_NAVIGATION_INTERCEPTION_INTERCEPT_NAVIGATION_THROTTLE_H_
 #define COMPONENTS_NAVIGATION_INTERCEPTION_INTERCEPT_NAVIGATION_THROTTLE_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 13 matching lines @@
 
 // This class allows the provider of the Callback to selectively ignore top
 // level navigations. This is a UI thread class.
 class InterceptNavigationThrottle : public content::NavigationThrottle {
  public:
   typedef base::Callback<bool(content::WebContents* /* source */,
                               const NavigationParams& /* navigation_params */)>
       CheckCallback;
 
   InterceptNavigationThrottle(content::NavigationHandle* navigation_handle,
-                              CheckCallback should_ignore_callback);
+                              CheckCallback should_ignore_callback,
+                              bool run_callback_synchronously);
   ~InterceptNavigationThrottle() override;
 
   // content::NavigationThrottle implementation:
   ThrottleCheckResult WillStartRequest() override;
   ThrottleCheckResult WillRedirectRequest() override;
 
  private:
   ThrottleCheckResult CheckIfShouldIgnoreNavigation(bool is_redirect);
 
+  // Called to perform the checks asynchronously
+  void RunCallbackAsynchronously(const NavigationParams& navigation_params);
+  void OnAsynchronousChecksPerformed(bool should_ignore_navigation);
+
   CheckCallback should_ignore_callback_;
 
+  // Whether the callback will be run synchronously or not. If the callback can
+  // lead to the destruction of the WebContents, this should be false.
+  // Otherwise this should be true.
+  const bool run_callback_synchronously_;
+
+  base::WeakPtrFactory<InterceptNavigationThrottle> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(InterceptNavigationThrottle);
 };
 
 }  // namespace navigation_interception
 
 #endif  // COMPONENTS_NAVIGATION_INTERCEPTION_INTERCEPT_NAVIGATION_THROTTLE_H_