Bug 1032646 - Record discovery replies to avoid purging every time. r=paul

toolkit/devtools/discovery/discovery.js

@@ -329,6 +329,9 @@ Discovery.prototype = {
     let remoteDevice = update.device;
     let remoteHost = update.from;
 
+    // Record the reply as received so it won't be purged as missing
+    this._expectingReplies.from.delete(remoteDevice);
+
     // First, loop over the known services
     for (let service in this.remoteServices) {
       let devicesWithService = this.remoteServices[service];

toolkit/devtools/discovery/tests/unit/test_discovery.js

@@ -116,6 +116,9 @@ add_task(function*() {
   discovery.addService("penguins", { tux: false });
   yield scanForChange("penguins", "updated");
 
+  // Scan again, but nothing should be removed
+  yield scanForNoChange("penguins", "removed");
+
   // Split the scanning side from the service side to simulate the machine with
   // the service becoming unreachable
   gTestTransports = {};
@@ -137,3 +140,17 @@ function scanForChange(service, changeType) {
   discovery.scan();
   return deferred.promise;
 }
+
+function scanForNoChange(service, changeType) {
+  let deferred = promise.defer();
+  let timer = setTimeout(() => {
+    deferred.resolve();
+  }, discovery.replyTimeout + 500);
+  discovery.on(service + "-device-" + changeType, function onChange() {
+    discovery.off(service + "-device-" + changeType, onChange);
+    clearTimeout(timer);
+    deferred.reject(new Error("Unexpected change occurred"));
+  });
+  discovery.scan();
+  return deferred.promise;
+}