Factor out some common logic from the launchers.

lib/src/runner/browser/safari.dart

Index: lib/src/runner/browser/safari.dart
diff --git a/lib/src/runner/browser/safari.dart b/lib/src/runner/browser/safari.dart
index 20f4e39ecd6f880f214d7d17c960191c4297ec92..e600e00e6ea77a3bfcafc3af05e5f4806931d1db 100644
--- a/lib/src/runner/browser/safari.dart
+++ b/lib/src/runner/browser/safari.dart
@@ -9,82 +9,43 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
-import 'package:stack_trace/stack_trace.dart';
 
 import '../../util/io.dart';
-import '../../utils.dart';
-import '../application_exception.dart';
 import 'browser.dart';
 
 /// A class for running an instance of Safari.
 ///
 /// Any errors starting or running the process are reported through [onExit].
-class Safari implements Browser {
-  /// The underlying process.
-  Process _process;
+class Safari extends Browser {
+  final name = "Safari";
 
-  Future get onExit => _onExitCompleter.future;
-  final _onExitCompleter = new Completer();
-
-  /// A future that completes when the browser process has started.
-  ///
-  /// This is used to ensure that [close] works regardless of when it's called.
-  Future get _onProcessStarted => _onProcessStartedCompleter.future;
-  final _onProcessStartedCompleter = new Completer();
+  Safari(url, {String executable})
+      : super(() => _startBrowser(url, executable));
 
   /// Starts a new instance of Safari open to the given [url], which may be a
   /// [Uri] or a [String].
   ///
-  /// If [executable] is passed, it's used as the Safari executable. Otherwise
-  /// the default executable name for the current OS will be used.
-  Safari(url, {String executable}) {
+  /// If [executable] is passed, it's used as the content shell executable.
+  /// Otherwise the default executable name for the current OS will be used.
+  static Future<Process> _startBrowser(url, [String executable]) async {
     if (executable == null) {
       executable = '/Applications/Safari.app/Contents/MacOS/Safari';
     }
 
-    // Don't return a Future here because there's no need for the caller to wait
-    // for the process to actually start. They should just wait for the HTTP
-    // request instead.
-    invoke(() async {
-      try {
-        var exitCode = await withTempDir((dir) async {
-          // Safari will only open files (not general URLs) via the command-line
-          // API, so we create a dummy file to redirect it to the page we actually
-          // want it to load.
-          var redirect = p.join(dir, 'redirect.html');
-          new File(redirect).writeAsStringSync(
-              "<script>location = " + JSON.encode(url.toString()) + "</script>");
-
-          var process = await Process.start(executable, [redirect]);
-          _process = process;
-          _onProcessStartedCompleter.complete();
+    var dir = createTempDir();
 
-          // TODO(nweiz): the browser's standard output is almost always useless
-          // noise, but we should allow the user to opt in to seeing it.
-          return await _process.exitCode;
-        });
+    // Safari will only open files (not general URLs) via the command-line
+    // API, so we create a dummy file to redirect it to the page we actually
+    // want it to load.
+    var redirect = p.join(dir, 'redirect.html');
+    new File(redirect).writeAsStringSync(
+        "<script>location = " + JSON.encode(url.toString()) + "</script>");
 
-        if (exitCode != 0) {
-          var error = await UTF8.decodeStream(_process.stderr);
-          throw new ApplicationException(
-              "Safari failed with exit code $exitCode:\n$error");
-        }
-
-        _onExitCompleter.complete();
-      } catch (error, stackTrace) {
-        if (stackTrace == null) stackTrace = new Trace.current();
-        _onExitCompleter.completeError(
-            new ApplicationException(
-                "Failed to start Safari: ${getErrorMessage(error)}."),
-            stackTrace);
-      }
-    });
-  }
+    var process = await Process.start(executable, [redirect]);
 
-  Future close() {
-    _onProcessStarted.then((_) => _process.kill());
+    process.exitCode
+        .then((_) => new Directory(dir).deleteSync(recursive: true));
 
-    // Swallow exceptions. The user should explicitly use [onExit] for these.
-    return onExit.catchError((_) {});
+    return process;
   }
 }