Stop working around issue 6775.

pkg/oauth2/lib/src/credentials.dart

 // Copyright (c) 2012, 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 credentials;
 
 import 'dart:async';
 import 'dart:json' as JSON;
 
 import 'package:http/http.dart' as http;
@@ skipping 63 matching lines @@
   factory Credentials.fromJson(String json) {
     void validate(bool condition, String message) {
       if (condition) return;
       throw new FormatException(
           "Failed to load credentials: $message.\n\n$json");
     }
 
     var parsed;
     try {
       parsed = JSON.parse(json);
-    } catch (e) {
-      // TODO(nweiz): narrow this catch clause once issue 6775 is fixed.
+    } on FormatException catch (e) {
       validate(false, 'invalid JSON');
     }
 
     validate(parsed is Map, 'was not a JSON map');
     validate(parsed.containsKey('accessToken'),
         'did not contain required field "accessToken"');
     validate(parsed['accessToken'] is String,
         'required field "accessToken" was not a string, was '
         '${parsed["accessToken"]}');
 
@@ skipping 88 matching lines @@
       if (credentials.refreshToken != null) return credentials;
       return new Credentials(
           credentials.accessToken,
           this.refreshToken,
           credentials.tokenEndpoint,
           credentials.scopes,
           credentials.expiration);
     });
   }
 }