Fix editor warnings in http_server and mime.

pkg/http_server/lib/src/http_body.dart

Index: pkg/http_server/lib/src/http_body.dart
diff --git a/pkg/http_server/lib/src/http_body.dart b/pkg/http_server/lib/src/http_body.dart
index 3efaadf3c352e97e098109cdc775b1410408796f..422f9dcb0e658c7b10741054901741a0329b6eff 100644
--- a/pkg/http_server/lib/src/http_body.dart
+++ b/pkg/http_server/lib/src/http_body.dart
@@ -223,16 +223,16 @@ abstract class HttpBodyFileUpload {
   /**
    * The filename of the uploaded file.
    */
-  String filename;
+  String get filename;
 
   /**
    * The [ContentType] of the uploaded file. For 'text/\*' and
    * 'application/json' the [data] field will a String.
    */
-  ContentType contentType;
+  ContentType get contentType;
 
   /**
    * The content of the file. Either a [String] or a [List<int>].
    */
-  dynamic content;
+  dynamic get content;
 }