add baseBlock comment, fix referencing befor StateAt

Author: magicxyyz

eth/state_accessor.go

@@ -47,6 +47,7 @@ import (
 //   - reexec:     The maximum number of blocks to reprocess trying to obtain the desired state
 //   - base:       If the caller is tracing multiple blocks, the caller can provide the parent
 //     state continuously from the callsite.
+//   - baseBlock:  Arbitrum specific: caller can provide the block from which reprocessing should start. Previous argument (base) is assumed to be the state at the block. If base is not provided, baseBlock is ignored.
 //   - readOnly:   If true, then the live 'blockchain' state database is used. No mutation should
 //     be made from caller, e.g. perform Commit or other 'save-to-disk' changes.
 //     Otherwise, the trash generated by caller may be persisted permanently.
@@ -68,7 +69,7 @@ func (eth *Ethereum) StateAtBlock(ctx context.Context, block *types.Block, reexe
 		// function to deref it.
 
 		// Try referencing the root, if it isn't in dirties cache then Reference will have no effect
-		statedb.Database().TrieDB().Reference(block.Root(), common.Hash{})
+		eth.blockchain.StateCache().TrieDB().Reference(block.Root(), common.Hash{})
 		if statedb, err = eth.blockchain.StateAt(block.Root()); err == nil {
 			return statedb, func() {
 				statedb.Database().TrieDB().Dereference(block.Root())