Made pendingHeaderCh buffered on the pendingHeaderFeed subscription

This has improved the test performance, and more tolerant to small miner stalls

eth/filters/api.go

@@ -34,6 +34,10 @@ import (
 	"github.com/dominant-strategies/go-quai/rpc"
 )
 
+const (
+	c_pendingHeaderChSize = 20
+)
+
 // filter is a helper struct that holds meta information over the filter type
 // and associated subscription in the event system.
 type filter struct {
@@ -594,7 +598,7 @@ func (api *PublicFilterAPI) PendingHeader(ctx context.Context) (*rpc.Subscriptio
 	rpcSub := notifier.CreateSubscription()
 
 	go func() {
-		header := make(chan *types.Header)
+		header := make(chan *types.Header, c_pendingHeaderChSize)
 		headerSub := api.events.SubscribePendingHeader(header)
 
 		for {

eth/filters/filter_system.go

@@ -68,6 +68,8 @@ const (
 	logsChanSize = 10
 	// chainEvChanSize is the size of channel listening to ChainEvent.
 	chainEvChanSize = 10
+	// pendingHeaderChSize is the size of channel listening to PendingHeaderEvent.
+	pendingHeaderChSize = 20
 )
 
 type subscription struct {
@@ -126,7 +128,7 @@ func NewEventSystem(backend Backend, lightMode bool) *EventSystem {
 		rmLogsCh:        make(chan core.RemovedLogsEvent, rmLogsChanSize),
 		pendingLogsCh:   make(chan []*types.Log, logsChanSize),
 		chainCh:         make(chan core.ChainEvent, chainEvChanSize),
-		pendingHeaderCh: make(chan *types.Header),
+		pendingHeaderCh: make(chan *types.Header, pendingHeaderChSize),
 	}
 
 	nodeCtx := common.NodeLocation.Context()