Poll less frequently when own hidden service is stable.

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/BackoffFactory.java

@@ -1,7 +1,9 @@
 package org.briarproject.bramble.api.plugin;
 
+import org.briarproject.bramble.api.event.EventBus;
+
 public interface BackoffFactory {
 
-	Backoff createBackoff(int minInterval, int maxInterval,
-			double base);
+	Backoff createBackoff(EventBus eventBus, TransportId transportId,
+			int minInterval, int maxInterval, double base);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/PluginCallback.java

@@ -56,4 +56,9 @@ public interface PluginCallback extends ConnectionHandler {
 	 * This method can safely be called while holding a lock.
 	 */
 	void pluginStateChanged(State state);
+
+	/**
+	 * Informs the callback that the plugin's polling interval has decreased.
+	 */
+	void pollingIntervalDecreased();
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/event/PollingIntervalDecreasedEvent.java

@@ -0,0 +1,25 @@
+package org.briarproject.bramble.api.plugin.event;
+
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * An event that is broadcast when a plugin's polling interval decreases.
+ */
+@Immutable
+@NotNullByDefault
+public class PollingIntervalDecreasedEvent extends Event {
+
+	private final TransportId transportId;
+
+	public PollingIntervalDecreasedEvent(TransportId transportId) {
+		this.transportId = transportId;
+	}
+
+	public TransportId getTransportId() {
+		return transportId;
+	}
+}