Properly report load errors caused by browsers.

lib/src/runner/browser/server.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library test.runner.browser.server;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
+import 'package:async/async.dart';
 import 'package:http_multi_server/http_multi_server.dart';
 import 'package:path/path.dart' as p;
 import 'package:pool/pool.dart';
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:shelf/shelf_io.dart' as shelf_io;
 import 'package:shelf_static/shelf_static.dart';
 import 'package:shelf_web_socket/shelf_web_socket.dart';
 
 import '../../backend/metadata.dart';
 import '../../backend/suite.dart';
@@ skipping 106 matching lines @@
 
   /// The thunk for running [close] exactly once.
   final _closeThunk = new AsyncThunk();
 
   /// All currently-running browsers.
   ///
   /// These are controlled by [_browserManager]s.
   final _browsers = new Map<TestPlatform, Browser>();
 
   /// A map from browser identifiers to futures that will complete to the
-  /// [BrowserManager]s for those browsers.
+  /// [BrowserManager]s for those browsers, or the errors that occurred when
+  /// trying to load those managers.
   ///
   /// This should only be accessed through [_browserManagerFor].
-  final _browserManagers = new Map<TestPlatform, Future<BrowserManager>>();
+  final _browserManagers =
+      new Map<TestPlatform, Future<Result<BrowserManager>>>();
 
   /// A map from test suite paths to Futures that will complete once those
   /// suites are finished compiling.
   ///
   /// This is used to make sure that a given test suite is only compiled once
   /// per run, rather than once per browser per run.
   final _compileFutures = new Map<String, Future>();
 
   final _mappers = new Map<String, StackTraceMapper>();
 
@@ skipping 250 matching lines @@
           packageRoot: p.toUri(_packageRoot),
           sdkRoot: p.toUri(sdkDir));
     });
   }
 
   /// Returns the [BrowserManager] for [platform], which should be a browser.
   ///
   /// If no browser manager is running yet, starts one.
   Future<BrowserManager> _browserManagerFor(TestPlatform platform) {
     var manager = _browserManagers[platform];
-    if (manager != null) return manager;
+    if (manager != null) return Result.release(manager);
 
     var completer = new Completer();
 
-    // Swallow errors, since they're already being surfaced through the return
-    // value and [browser.onError].
-    _browserManagers[platform] = completer.future.catchError((_) {});
+    // Capture errors and release them later to avoid Zone issues. This call to
+    // [_browserManagerFor] is running in a different [LoadSuite] than future
+    // calls, which means they're also running in different error zones so
+    // errors can't be freely passed between them. Storing the error or value as
+    // an explicit [Result] fixes that.
+    _browserManagers[platform] = Result.capture(completer.future);
     var path = _webSocketHandler.create(webSocketHandler((webSocket) {
       completer.complete(new BrowserManager(platform, webSocket));
     }));
 
     var webSocketUrl = url.replace(scheme: 'ws').resolve(path);
 
     var hostUrl = (_pubServeUrl == null ? url : _pubServeUrl)
         .resolve('packages/test/src/runner/browser/static/index.html');
 
     var browser = _newBrowser(hostUrl.replace(queryParameters: {
@@ skipping 47 matching lines @@
       await Future.wait(futures);
 
       if (_pubServeUrl == null) {
         new Directory(_compiledDir).deleteSync(recursive: true);
       } else {
         _http.close();
       }
     });
   }
 }