Implement several btcd RPCs in wallet as well.

Wallet should handle these so that wallet clients don't end up
creating requests to btcd about the latest processed block, which is
not the same as wallet's most recently processed block.

By providing wallet clients with this info, we avoid a race where the
client thinks wallet has processed N blocks, but in fact is still
synced to N-1 (and perhaps currently processing transactions from
block N).  This can cause unexpected results for many of the
bitcoind-compatible RPC APIs due to their reliance on number of
confirmations, rather than using absolute block heights.

rpcserver.go

@@ -1361,6 +1361,8 @@ var rpcHandlers = map[string]requestHandler{
 	"getaccountaddress":      GetAccountAddress,
 	"getaddressesbyaccount":  GetAddressesByAccount,
 	"getbalance":             GetBalance,
+	"getbestblockhash":       GetBestBlockHash,
+	"getblockcount":          GetBlockCount,
 	"getinfo":                GetInfo,
 	"getnewaddress":          GetNewAddress,
 	"getrawchangeaddress":    GetRawChangeAddress,
@@ -1404,6 +1406,7 @@ var rpcHandlers = map[string]requestHandler{
 
 	// Extensions to the reference client JSON-RPC API
 	"exportwatchingwallet": ExportWatchingWallet,
+	"getbestblock":         GetBestBlock,
 	// This was an extension but the reference implementation added it as
 	// well, but with a different API (no account parameter).  It's listed
 	// here because it hasn't been update to use the reference
@@ -1717,6 +1720,31 @@ func GetBalance(w *Wallet, chainSvr *chain.Client, icmd btcjson.Cmd) (interface{
 	return balance.ToUnit(btcutil.AmountBTC), nil
 }
 
+// GetBestBlock handles a getbestblock request by returning a JSON object
+// with the height and hash of the most recently processed block.
+func GetBestBlock(w *Wallet, chainSvr *chain.Client, icmd btcjson.Cmd) (interface{}, error) {
+	blk := w.Manager.SyncedTo()
+	result := &btcws.GetBestBlockResult{
+		Hash:   blk.Hash.String(),
+		Height: blk.Height,
+	}
+	return result, nil
+}
+
+// GetBestBlockHash handles a getbestblockhash request by returning the hash
+// of the most recently processed block.
+func GetBestBlockHash(w *Wallet, chainSvr *chain.Client, icmd btcjson.Cmd) (interface{}, error) {
+	blk := w.Manager.SyncedTo()
+	return blk.Hash.String(), nil
+}
+
+// GetBlockCount handles a getblockcount request by returning the chain height
+// of the most recently processed block.
+func GetBlockCount(w *Wallet, chainSvr *chain.Client, icmd btcjson.Cmd) (interface{}, error) {
+	blk := w.Manager.SyncedTo()
+	return blk.Height, nil
+}
+
 // GetInfo handles a getinfo request by returning the a structure containing
 // information about the current state of btcwallet.
 // exist.

wallet.go

@@ -425,7 +425,7 @@ func (w *Wallet) syncWithChain() (err error) {
 			w.Manager.SetSyncedTo(&bs)
 			err = w.TxStore.Rollback(bs.Height)
 			if err != nil {
-				return
+				return err
 			}
 			w.TxStore.MarkDirty()
 		}