[Sync] Add plumbing of context from client to server

sync/engine/directory_commit_contribution.h

Index: sync/engine/directory_commit_contribution.h
diff --git a/sync/engine/directory_commit_contribution.h b/sync/engine/directory_commit_contribution.h
index 508ac7c6a1f2875d226a1026b45b8d460f1c5f99..ec58ed56436d8f87f2de1181496c58c26b8cec3b 100644
--- a/sync/engine/directory_commit_contribution.h
+++ b/sync/engine/directory_commit_contribution.h
@@ -66,7 +66,7 @@ class SYNC_EXPORT_PRIVATE DirectoryCommitContribution
       const sync_pb::ClientToServerResponse& response,
       sessions::StatusController* status) OVERRIDE;
 
-  // Cleans up any temproary state associated with the commit.  Must be called
+  // Cleans up any temporary state associated with the commit.  Must be called
   // before destruction.
   virtual void CleanUp() OVERRIDE;
 
@@ -80,6 +80,7 @@ class SYNC_EXPORT_PRIVATE DirectoryCommitContribution
                            GatherAndTruncate);
 
   DirectoryCommitContribution(
+      ModelType type,
       const std::vector<int64>& metahandles,
       const google::protobuf::RepeatedPtrField<sync_pb::SyncEntity>& entities,
       syncable::Directory* directory);
@@ -87,6 +88,7 @@ class SYNC_EXPORT_PRIVATE DirectoryCommitContribution
   void UnsetSyncingBits();
 
   syncable::Directory* dir_;
+  ModelType type_;
   const std::vector<int64> metahandles_;
   const google::protobuf::RepeatedPtrField<sync_pb::SyncEntity> entities_;
   size_t entries_start_index_;