Add auto-detection of MIME-type in VirtualDirectory.

pkg/http_server/test/virtual_directory_test.dart

 // Copyright (c) 2013, 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.
 
 import 'dart:async';
 import 'dart:io';
 
 import "package:unittest/unittest.dart";
 import "package:http_server/http_server.dart";
 
@@ skipping 212 matching lines @@
                 .whenComplete(() {
                   server.close();
                   dir.deleteSync(recursive: true);
                 });
           }), completion(equals(HttpStatus.NOT_FOUND)));
         });
       });
     }
   });
 
-  group('last-mofidied', () {
+  group('last-modified', () {
     group('file', () {
       test('file-exists', () {
         expect(HttpServer.bind('localhost', 0).then((server) {
           var dir = new Directory('').createTempSync();
           var file = new File('${dir.path}/file')..createSync();
           var virDir = new VirtualDirectory(dir.path);
 
           virDir.serve(server);
 
           return getHeaders(server.port, '/file')
@@ skipping 35 matching lines @@
                     server.port, '/file', ifModifiedSince: lastModified);
               })
               .whenComplete(() {
                 server.close();
                 dir.deleteSync(recursive: true);
               });
         }), completion(equals(HttpStatus.OK)));
       });
     });
   });
+
+  group('content-type', () {
+    group('mime-type', () {
+      test('from-path', () {
+        expect(HttpServer.bind('localhost', 0).then((server) {
+          var dir = new Directory('').createTempSync();
+          var file = new File('${dir.path}/file.jpg')..createSync();
+          var virDir = new VirtualDirectory(dir.path);
+
+          virDir.serve(server);
+
+          return getHeaders(server.port, '/file.jpg')
+              .then((headers) => headers.contentType.toString())
+              .whenComplete(() {
+                server.close();
+                dir.deleteSync(recursive: true);
+              });
+        }), completion(equals('image/jpeg')));
+      });
+
+      test('from-magic-number', () {
+        expect(HttpServer.bind('localhost', 0).then((server) {
+          var dir = new Directory('').createTempSync();
+          var file = new File('${dir.path}/file.jpg')..createSync();
+          file.writeAsBytesSync(
+              [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A]);
+          var virDir = new VirtualDirectory(dir.path);
+
+          virDir.serve(server);
+
+          return getHeaders(server.port, '/file.jpg')
+              .then((headers) => headers.contentType.toString())
+              .whenComplete(() {
+                server.close();
+                dir.deleteSync(recursive: true);
+              });
+        }), completion(equals('image/png')));
+      });
+    });
+  });
 }