Allow weird characters (like ?) to appear in devfs filenames.

runtime/observatory/tests/service/dev_fs_test.dart

 // Copyright (c) 2016, 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.
 // VMOptions=--error_on_bad_type --error_on_bad_override
 
 import 'dart:convert';
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
@@ skipping 135 matching lines @@
     });
     expect(result['type'], equals('FSFileList'));
     expect(result['files'].length, equals(3));
 
     // Delete DevFS.
     result = await vm.invokeRpcNoUpgrade('_deleteDevFS', {
         'fsName': fsId,
     });
     expect(result['type'], equals('Success'));
   },
+
+  // Write a file with the ? character in the filename.
+  (VM vm) async {
+    var fsId = 'test';
+    var filePath = '/foo/bar?dat';
+    var fileContents = BASE64.encode(UTF8.encode('fileContents'));
+
+    var result;
+    // Create DevFS.
+    result = await vm.invokeRpcNoUpgrade('_createDevFS', { 'fsName': fsId });
+    expect(result['type'], equals('FileSystem'));
+    expect(result['name'], equals(fsId));
+    expect(result['uri'], new isInstanceOf<String>());
+
+    // Write the file.
+    result = await vm.invokeRpcNoUpgrade('_writeDevFSFile', {
+        'fsName': fsId,
+        'path': filePath,
+        'fileContents': fileContents
+    });
+    expect(result['type'], equals('Success'));
+
+    // Read the file back.
+    result = await vm.invokeRpcNoUpgrade('_readDevFSFile', {
+        'fsName': fsId,
+        'path': filePath,
+    });
+    expect(result['type'], equals('FSFile'));
+    expect(result['fileContents'], equals(fileContents));
+
+    // List all the files in the file system.
+    result = await vm.invokeRpcNoUpgrade('_listDevFSFiles', {
+        'fsName': fsId,
+    });
+    expect(result['type'], equals('FSFileList'));
+    expect(result['files'].length, equals(1));
+    expect(result['files'][0]['name'], equals('/foo/bar?dat'));
+
+    // Delete DevFS.
+    result = await vm.invokeRpcNoUpgrade('_deleteDevFS', {
+        'fsName': fsId,
+    });
+    expect(result['type'], equals('Success'));
+  },
 ];
 
 main(args) async => runVMTests(args, tests);