channelnotifier: let notifier take channel updates

diff --git a/channelnotifier/channelnotifier.go b/channelnotifier/channelnotifier.go
index f13ca6d..e7b815b 100644
--- a/channelnotifier/channelnotifier.go
+++ b/channelnotifier/channelnotifier.go
@@ -72,6 +72,12 @@ type ClosedChannelEvent struct {
 	CloseSummary *channeldb.ChannelCloseSummary
 }
 
+// ChannelUpdateEvent represents a new event where a channel's state is updated.
+type ChannelUpdateEvent struct {
+	// Channel is the channel that has been updated.
+	Channel *channeldb.OpenChannel
+}
+
 // FullyResolvedChannelEvent represents a new event where a channel becomes
 // fully resolved.
 type FullyResolvedChannelEvent struct {
@@ -238,3 +244,14 @@ func (c *ChannelNotifier) NotifyInactiveChannelEvent(chanPoint wire.OutPoint) {
 		log.Warnf("Unable to send inactive channel update: %v", err)
 	}
 }
+
+// NotifyChannelUpdateEvent notifies subscribers that a channel's state has been
+// updated.
+func (c *ChannelNotifier) NotifyChannelUpdateEvent(
+	channel *channeldb.OpenChannel) {
+
+	event := ChannelUpdateEvent{Channel: channel}
+	if err := c.ntfnServer.SendUpdate(event); err != nil {
+		log.Warnf("Unable to send channel update: %v", err)
+	}
+}
diff --git a/channelnotifier/channelnotifier_test.go b/channelnotifier/channelnotifier_test.go
new file mode 100644
index 0000000..5dbdb4a
--- /dev/null
+++ b/channelnotifier/channelnotifier_test.go
@@ -0,0 +1,43 @@
+package channelnotifier
+
+import (
+	"testing"
+	"time"
+
+	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/stretchr/testify/require"
+)
+
+// TestChannelUpdateEvent tests that channel update events are properly
+// notified to subscribers.
+func TestChannelUpdateEvent(t *testing.T) {
+	// Initialize the notification server.
+	ntfnServer := New(nil)
+	require.NoError(t, ntfnServer.Start())
+
+	defer func() {
+		require.NoError(t, ntfnServer.Stop())
+	}()
+
+	// Subscribe to channel events.
+	sub, err := ntfnServer.SubscribeChannelEvents()
+	require.NoError(t, err)
+	defer sub.Cancel()
+
+	// Create a mock channel state.
+	channel := &channeldb.OpenChannel{}
+
+	// Notify the server of a channel update event.
+	ntfnServer.NotifyChannelUpdateEvent(channel)
+
+	// Consume the event.
+	select {
+	case event := <-sub.Updates():
+		updateEvent, ok := event.(ChannelUpdateEvent)
+		require.True(t, ok)
+		require.Equal(t, channel, updateEvent.Channel)
+
+	case <-time.After(time.Second):
+		t.Fatalf("expected to receive channel update event")
+	}
+}