Provide API in RequestCoordinator to remove results by client ID.

components/offline_pages/background/request_coordinator.cc

Index: components/offline_pages/background/request_coordinator.cc
diff --git a/components/offline_pages/background/request_coordinator.cc b/components/offline_pages/background/request_coordinator.cc
index 13ab786e6ef39a623022bb3190f01917e1410029..9100547bd2262927ee827dbdb564dc4fa3203481 100644
--- a/components/offline_pages/background/request_coordinator.cc
+++ b/components/offline_pages/background/request_coordinator.cc
@@ -70,6 +70,16 @@ bool RequestCoordinator::SavePageLater(
   return true;
 }
 
+// If the client does not need the pages after all, then cancel them.
+void RequestCoordinator::CancelRequests(
+    const std::vector<ClientId>& client_ids) {
+
+  queue_->RemoveRequestsByClientId(
+      client_ids,
+      base::Bind(&RequestCoordinator::UpdateRequestCallback,
+                 weak_ptr_factory_.GetWeakPtr()));
+}
+
 void RequestCoordinator::AddRequestResultCallback(
     RequestQueue::AddRequestResult result,
     const SavePageRequest& request) {