Remove derivation based extensibility points.

src/Microsoft.AspNet.Mvc/ActionResults/JsonResult.cs

@@ -12,7 +12,7 @@ namespace Microsoft.AspNet.Mvc
         private readonly object _returnValue;
 
         private JsonSerializerSettings _jsonSerializerSettings;
-        private Encoding _encoding;
+        private Encoding _encoding = Encoding.UTF8;
 
         public JsonResult(object returnValue)
         {
@@ -21,8 +21,6 @@ namespace Microsoft.AspNet.Mvc
                 throw new ArgumentNullException("returnValue");
             }
 
-            Encoding = Encoding.UTF8;
-
             _returnValue = returnValue;
             _jsonSerializerSettings = CreateSerializerSettings();
         }
@@ -61,43 +59,16 @@ namespace Microsoft.AspNet.Mvc
             }
         }
 
-        public virtual JsonSerializerSettings CreateSerializerSettings()
-        {
-            return new JsonSerializerSettings()
-            {
-                MissingMemberHandling = MissingMemberHandling.Ignore,
-
-                // Do not change this setting
-                // Setting this to None prevents Json.NET from loading malicious, unsafe, or security-sensitive types.
-                TypeNameHandling = TypeNameHandling.None
-            };
-        }
-
-        public virtual JsonSerializer CreateJsonSerializer()
-        {
-            JsonSerializer jsonSerializer = JsonSerializer.Create(SerializerSettings);
-
-            return jsonSerializer;
-        }
-
-        public virtual JsonWriter CreateJsonWriter(Stream writeStream, Encoding effectiveEncoding)
-        {
-            JsonWriter jsonWriter = new JsonTextWriter(new StreamWriter(writeStream, effectiveEncoding));
-            if (Indent)
-            {
-                jsonWriter.Formatting = Formatting.Indented;
-            }
-
-            return jsonWriter;
-        }
-
         public async Task ExecuteResultAsync(RequestContext context)
         {
             HttpResponse response = context.HttpContext.Response;
 
             Stream writeStream = response.Body;
 
-            response.ContentType = "application/json";
+            if (response.ContentType == null)
+            {
+                response.ContentType = "application/json";
+            }
 
             using (JsonWriter jsonWriter = CreateJsonWriter(writeStream, Encoding))
             {
@@ -109,5 +80,35 @@ namespace Microsoft.AspNet.Mvc
                 jsonWriter.Flush();
             }
         }
+
+        private JsonSerializerSettings CreateSerializerSettings()
+        {
+            return new JsonSerializerSettings()
+            {
+                MissingMemberHandling = MissingMemberHandling.Ignore,
+
+                // Do not change this setting
+                // Setting this to None prevents Json.NET from loading malicious, unsafe, or security-sensitive types.
+                TypeNameHandling = TypeNameHandling.None
+            };
+        }
+
+        private JsonSerializer CreateJsonSerializer()
+        {
+            JsonSerializer jsonSerializer = JsonSerializer.Create(SerializerSettings);
+
+            return jsonSerializer;
+        }
+
+        private JsonWriter CreateJsonWriter(Stream writeStream, Encoding effectiveEncoding)
+        {
+            JsonWriter jsonWriter = new JsonTextWriter(new StreamWriter(writeStream, effectiveEncoding));
+            if (Indent)
+            {
+                jsonWriter.Formatting = Formatting.Indented;
+            }
+
+            return jsonWriter;
+        }
     }
 }