[Sync] Maintain a global_id mapping to update UserEvents that references navigations

components/sync/user_events/user_event_sync_bridge.h

Index: components/sync/user_events/user_event_sync_bridge.h
diff --git a/components/sync/user_events/user_event_sync_bridge.h b/components/sync/user_events/user_event_sync_bridge.h
index 8f2409a5a03fa0a979f1cbfbca6e141b3bbab090..bbdef87b8604accc209fd9cd1794ee5b859c80fa 100644
--- a/components/sync/user_events/user_event_sync_bridge.h
+++ b/components/sync/user_events/user_event_sync_bridge.h
@@ -5,19 +5,24 @@
 #ifndef COMPONENTS_SYNC_USER_EVENTS_USER_EVENT_SYNC_BRIDGE_H_
 #define COMPONENTS_SYNC_USER_EVENTS_USER_EVENT_SYNC_BRIDGE_H_
 
+#include <stdint.h>
+
+#include <map>
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "components/sync/model/model_type_store.h"
 #include "components/sync/model/model_type_sync_bridge.h"
+#include "components/sync/user_events/global_id_mapper.h"
 
 namespace syncer {
 
 class UserEventSyncBridge : public ModelTypeSyncBridge {
  public:
   UserEventSyncBridge(const ModelTypeStoreFactory& store_factory,
-                      const ChangeProcessorFactory& change_processor_factory);
+                      const ChangeProcessorFactory& change_processor_factory,
+                      GlobalIdMapper* global_id_mapper);
   ~UserEventSyncBridge() override;
 
   // ModelTypeSyncBridge implementation.
@@ -53,10 +58,18 @@ class UserEventSyncBridge : public ModelTypeSyncBridge {
       ModelTypeStore::Result result,
       std::unique_ptr<ModelTypeStore::RecordList> data_records);
 
+  void HandleGlobalIdChange(int64_t old_global_id, int64_t new_global_id);
+
   // Persistent storage for in flight events. Should remain quite small, as we
   // delete upon commit confirmation.
   std::unique_ptr<ModelTypeStore> store_;
 
+  // The key is the global_id of the navigation the event is linked to.
+  std::multimap<int64_t, sync_pb::UserEventSpecifics>
+      in_flight_nav_linked_events_;
+
+  GlobalIdMapper* global_id_mapper_;
+
   DISALLOW_COPY_AND_ASSIGN(UserEventSyncBridge);
 };