Add the ability to cancel prerender reqeusts and tests

components/offline_pages/background/request_coordinator.h

Index: components/offline_pages/background/request_coordinator.h
diff --git a/components/offline_pages/background/request_coordinator.h b/components/offline_pages/background/request_coordinator.h
index ffbb8570499257b13d5d6f8b66ab650d85d5e887..1cac7ff0fd74615d82c98fc6a29bd3139817f76c 100644
--- a/components/offline_pages/background/request_coordinator.h
+++ b/components/offline_pages/background/request_coordinator.h
@@ -94,8 +94,16 @@ class RequestCoordinator : public KeyedService {
 
   void TryNextRequest();
 
+  void GetOffliner();
+
   friend class RequestCoordinatorTest;
 
+  // Unowned pointer to the offliner, if any.
+  Offliner* offliner_;
+  // True if a prerender has been started.
+  bool started_;
+  // True if a prerender request has been cancelled.
+  bool cancelled_;
   // RequestCoordinator takes over ownership of the policy
   std::unique_ptr<OfflinerPolicy> policy_;
   // OfflinerFactory.  Used to create offline pages. Owned.