Add a way to cancel deferred navigations in NavigationHandle

components/navigation_interception/intercept_navigation_throttle.h

Index: components/navigation_interception/intercept_navigation_throttle.h
diff --git a/components/navigation_interception/intercept_navigation_throttle.h b/components/navigation_interception/intercept_navigation_throttle.h
index 0b7f74605378266e5e09a549127d53639e1617a4..7ce296380e6c428b5939017b7acb873139aa18a9 100644
--- a/components/navigation_interception/intercept_navigation_throttle.h
+++ b/components/navigation_interception/intercept_navigation_throttle.h
@@ -31,7 +31,8 @@ class InterceptNavigationThrottle : public content::NavigationThrottle {
       CheckCallback;
 
   InterceptNavigationThrottle(content::NavigationHandle* navigation_handle,
-                              CheckCallback should_ignore_callback);
+                              CheckCallback should_ignore_callback,
+                              bool run_callback_synchronously);
   ~InterceptNavigationThrottle() override;
 
   // content::NavigationThrottle implementation:
@@ -41,8 +42,19 @@ class InterceptNavigationThrottle : public content::NavigationThrottle {
  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);
 };