Clean up the warning for unknown tags.

lib/src/runner/load_suite.dart

Index: lib/src/runner/load_suite.dart
diff --git a/lib/src/runner/load_suite.dart b/lib/src/runner/load_suite.dart
index a83177746f0ddd81202ef33bd62b0a1d644e6c34..cb84a0b5121ee73be5211249f04013de2bc69c7d 100644
--- a/lib/src/runner/load_suite.dart
+++ b/lib/src/runner/load_suite.dart
@@ -39,7 +39,13 @@ class LoadSuite extends RunnerSuite {
   ///
   /// This will return `null` if the suite is unavailable for some reason (for
   /// example if an error occurred while loading it).
-  final Future<RunnerSuite> suite;
+  Future<RunnerSuite> get suite async => (await _suiteAndZone)?.first;
+
+  /// A future that completes to a pair of [suite] and the load test's [Zone].
+  ///
+  /// This will return `null` if the suite is unavailable for some reason (for
+  /// example if an error occurred while loading it).
+  final Future<Pair<RunnerSuite, Zone>> _suiteAndZone;
 
   /// Returns the test that loads the suite.
   ///
@@ -71,7 +77,7 @@ class LoadSuite extends RunnerSuite {
             return;
           }
 
-          completer.complete(suite);
+          completer.complete(new Pair(suite, Zone.current));
           invoker.removeOutstandingCallback();
         } catch (error, stackTrace) {
           registerException(error, stackTrace);
@@ -107,7 +113,8 @@ class LoadSuite extends RunnerSuite {
         platform: suite.platform);
   }
 
-  LoadSuite._(String name, void body(), this.suite, {TestPlatform platform})
+  LoadSuite._(String name, void body(), this._suiteAndZone,
+          {TestPlatform platform})
       : super(const VMEnvironment(), new Group.root([
         new LocalTest(name,
             new Metadata(timeout: new Timeout(new Duration(minutes: 5))),
@@ -115,17 +122,21 @@ class LoadSuite extends RunnerSuite {
       ]), platform: platform);
 
   /// A constructor used by [changeSuite].
-  LoadSuite._changeSuite(LoadSuite old, Future<RunnerSuite> this.suite)
+  LoadSuite._changeSuite(LoadSuite old, this._suiteAndZone)
       : super(const VMEnvironment(), old.group, platform: old.platform);
 
   /// Creates a new [LoadSuite] that's identical to this one, but that
   /// transforms [suite] once it's loaded.
   ///
-  /// If [suite] completes to `null`, [change] won't be run.
+  /// If [suite] completes to `null`, [change] won't be run. [change] is run
+  /// within the load test's zone, so any errors or prints it emits will be
+  /// associated with that test.
   LoadSuite changeSuite(RunnerSuite change(RunnerSuite suite)) {
-    return new LoadSuite._changeSuite(this, suite.then((loadedSuite) {
-      if (loadedSuite == null) return null;
-      return change(loadedSuite);
+    return new LoadSuite._changeSuite(this, _suiteAndZone.then((pair) {
+      if (pair == null) return null;
+
+      var zone = pair.last;
+      return new Pair(zone.runUnaryGuarded(change, pair.first), zone);
     }));
   }