chainntnfs: add block cache to BtcdNotifier

This commit adds gives BtcdNotifier access to the block cache and wraps
its GetBlock method so that it uses the block cache.

chainntnfs/btcdnotify/driver.go

@@ -6,15 +6,16 @@ import (
 
 	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/btcsuite/btcd/rpcclient"
+	"github.com/lightningnetwork/lnd/blockcache"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 )
 
 // createNewNotifier creates a new instance of the ChainNotifier interface
 // implemented by BtcdNotifier.
 func createNewNotifier(args ...interface{}) (chainntnfs.ChainNotifier, error) {
-	if len(args) != 4 {
+	if len(args) != 5 {
 		return nil, fmt.Errorf("incorrect number of arguments to "+
-			".New(...), expected 4, instead passed %v", len(args))
+			".New(...), expected 5, instead passed %v", len(args))
 	}
 
 	config, ok := args[0].(*rpcclient.ConnConfig)
@@ -41,7 +42,15 @@ func createNewNotifier(args ...interface{}) (chainntnfs.ChainNotifier, error) {
 			"is incorrect, expected a chainntnfs.ConfirmHintCache")
 	}
 
-	return New(config, chainParams, spendHintCache, confirmHintCache)
+	blockCache, ok := args[4].(*blockcache.BlockCache)
+	if !ok {
+		return nil, errors.New("fifth argument to btcdnotify.New " +
+			"is incorrect, expected a *blockcache.BlockCache")
+	}
+
+	return New(
+		config, chainParams, spendHintCache, confirmHintCache, blockCache,
+	)
 }
 
 // init registers a driver for the BtcdNotifier concrete implementation of the