Migrate async tests to strong

tests/lib_strong/async/catch_errors.dart

+library catch_errors;
+
+import 'dart:async';
+
+Stream catchErrors(void body()) {
+  StreamController controller;
+
+  bool onError(e, st) {
+    controller.add(e);
+    return true;
+  }
+
+  void onListen() {
+    runZoned(body, onError: onError);
+  }
+
+  controller = new StreamController(onListen: onListen);
+  return controller.stream;
+}
+
+runZonedScheduleMicrotask(body(),
+                          { void onScheduleMicrotask(void callback()),
+                            Function onError }) {
+  if (onScheduleMicrotask == null) {
+    return runZoned(body, onError: onError);
+  }
+  HandleUncaughtErrorHandler errorHandler;
+  if (onError != null) {
+    errorHandler = (Zone self, ZoneDelegate parent, Zone zone,
+                    error, StackTrace stackTrace) {
+      try {
+        return self.parent.runUnary(onError, error);
+      } catch(e, s) {
+        if (identical(e, error)) {
+          return parent.handleUncaughtError(zone, error, stackTrace);
+        } else {
+          return parent.handleUncaughtError(zone, e, s);
+        }
+      }
+    };
+  }
+  ScheduleMicrotaskHandler asyncHandler;
+  if (onScheduleMicrotask != null) {
+    asyncHandler = (Zone self, ZoneDelegate parent, Zone zone, f()) {
+      self.parent.runUnary(onScheduleMicrotask, () => zone.runGuarded(f));
+    };
+  }
+  ZoneSpecification specification =
+      new ZoneSpecification(handleUncaughtError: errorHandler,
+                            scheduleMicrotask: asyncHandler);
+  Zone zone = Zone.current.fork(specification: specification);
+  if (onError != null) {
+    return zone.runGuarded(body);
+  } else {
+    return zone.run(body);
+  }
+}