[Sync] ModelTypeWorker should delete tracker for entity deleted on the server

components/sync/engine_impl/worker_entity_tracker.h

 // Copyright 2014 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_SYNC_ENGINE_IMPL_WORKER_ENTITY_TRACKER_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_WORKER_ENTITY_TRACKER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 22 matching lines @@
  public:
   // Initializes the entity tracker's main fields. Does not initialize state
   // related to a pending commit.
   explicit WorkerEntityTracker(const std::string& client_tag_hash);
 
   ~WorkerEntityTracker();
 
   // Returns true if this entity should be commited to the server.
   bool HasPendingCommit() const;
 
+  // Returns true if pending commit contains deleted entity.
+  bool PendingCommitIsDeletion() const;
+
   // Populates a sync_pb::SyncEntity for a commit.
   void PopulateCommitProto(sync_pb::SyncEntity* commit_entity) const;
 
   // Updates this entity with data from the latest version that the
   // model asked us to commit. May clobber state related to the
   // model's previous commit attempt(s).
   void RequestCommit(const CommitRequestData& data);
 
   // Tracks the receipt of a commit response and fills in some local-only data
   // on it to be passed back to the processor.
@@ skipping 65 matching lines @@
   // of an pending update prevents commits. As of this writing, the only
   // source of pending updates is updates that can't currently be decrypted.
   std::unique_ptr<UpdateResponseData> encrypted_update_;
 
   DISALLOW_COPY_AND_ASSIGN(WorkerEntityTracker);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_WORKER_ENTITY_TRACKER_H_