Fix dart2 constants
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1b37200..f26290f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 2.1.5
+
+- Require at least Dart 2.0.0-dev.61.
+
 ## 2.1.4
 - Require at least Dart 2.0.0.
 
diff --git a/lib/src/io_io.dart b/lib/src/io_io.dart
index edc0de6..f97b755 100644
--- a/lib/src/io_io.dart
+++ b/lib/src/io_io.dart
@@ -67,9 +67,9 @@
   if (uri.scheme == "http" || uri.scheme == "https") {
     HttpClientRequest request = await new HttpClient().getUrl(uri);
     // Prefer text/plain, text/* if possible, otherwise take whatever is there.
-    request.headers.set(HttpHeaders.ACCEPT, "text/plain, text/*, */*");
+    request.headers.set(HttpHeaders.acceptHeader, "text/plain, text/*, */*");
     if (encoding != null) {
-      request.headers.set(HttpHeaders.ACCEPT_CHARSET, encoding.name);
+      request.headers.set(HttpHeaders.acceptCharsetHeader, encoding.name);
     }
     HttpClientResponse response = await request.close();
     _throwIfFailed(response, uri);
@@ -99,13 +99,13 @@
 
 Future<HttpClientResponse> _httpGetBytes(Uri uri) async {
   HttpClientRequest request = await _sharedHttpClient.getUrl(uri);
-  request.headers.set(HttpHeaders.ACCEPT, "application/octet-stream, */*");
+  request.headers.set(HttpHeaders.acceptHeader, "application/octet-stream, */*");
   return request.close();
 }
 
 void _throwIfFailed(HttpClientResponse response, Uri uri) {
   var statusCode = response.statusCode;
-  if (statusCode < HttpStatus.OK || statusCode > HttpStatus.NO_CONTENT) {
+  if (statusCode < HttpStatus.ok || statusCode > HttpStatus.noContent) {
     throw new HttpException(response.reasonPhrase, uri: uri);
   }
 }
diff --git a/pubspec.yaml b/pubspec.yaml
index 2715e65..80b5c27 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,11 +1,11 @@
 name: resource
-version: 2.1.4
+version: 2.1.5-dev
 description: Reading resource data from (package and other) files.
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/resource
 
 environment:
-  sdk: '>=2.0.0-dev.17.0 <2.0.0'
+  sdk: '>=2.0.0-dev.61.0 <2.0.0'
 
 dependencies:
   typed_data: "^1.0.0"
diff --git a/test/loader_http_test.dart b/test/loader_http_test.dart
index a4b9de6..868f51d 100644
--- a/test/loader_http_test.dart
+++ b/test/loader_http_test.dart
@@ -23,11 +23,11 @@
     server.forEach((HttpRequest request) {
       if (request.uri.path.endsWith(".not")) {
         request.response
-          ..statusCode = HttpStatus.NOT_FOUND
+          ..statusCode = HttpStatus.notFound
           ..close();
         return;
       }
-      var encodings = request.headers[HttpHeaders.ACCEPT_CHARSET];
+      var encodings = request.headers[HttpHeaders.acceptCharsetHeader];
       var encoding = parseAcceptCharset(encodings);
       request.response.headers.contentType =
           new ContentType("text", "plain", charset: encoding.name);