Fix Snapshot restoration failure on Windows (#9491)

* Close Blooms DB files before DB restoration

* PR Grumbles I

* PR Grumble

* Grumble

ethcore/src/blockchain/blockchain.rs

@@ -35,6 +35,7 @@ use encoded;
 use engines::epoch::{Transition as EpochTransition, PendingTransition as PendingEpochTransition};
 use engines::ForkChoice;
 use ethereum_types::{H256, Bloom, BloomRef, U256};
+use error::Error as EthcoreError;
 use header::*;
 use heapsize::HeapSizeOf;
 use itertools::Itertools;
@@ -60,6 +61,21 @@ pub trait BlockChainDB: Send + Sync {
 
 	/// Trace blooms database.
 	fn trace_blooms(&self) -> &blooms_db::Database;
+
+	/// Restore the DB from the given path
+	fn restore(&self, new_db: &str) -> Result<(), EthcoreError> {
+		// First, close the Blooms databases
+		self.blooms().close()?;
+		self.trace_blooms().close()?;
+
+		// Restore the key_value DB
+		self.key_value().restore(new_db)?;
+
+		// Re-open the Blooms databases
+		self.blooms().reopen()?;
+		self.trace_blooms().reopen()?;
+		Ok(())
+	}
 }
 
 /// Generic database handler. This trait contains one function `open`. When called, it opens database with a