third_party/protobuf: Update to HEAD (83d681ee2c)

third_party/protobuf/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs

Index: third_party/protobuf/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs
diff --git a/third_party/protobuf/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs b/third_party/protobuf/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs
index 4bd62cf3d436bfa91dbeeb2485b15f6cbfd1a399..0685c21adfbda93ff34a5976cf97976bc36c97d8 100644
--- a/third_party/protobuf/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs
+++ b/third_party/protobuf/csharp/src/Google.Protobuf/WellKnownTypes/FieldMaskPartial.cs
@@ -52,14 +52,19 @@ namespace Google.Protobuf.WellKnownTypes
         /// </remarks>
         /// <param name="paths">Paths in the field mask</param>
         /// <param name="diagnosticOnly">Determines the handling of non-normalized values</param>
-        /// <exception cref="InvalidOperationException">The represented duration is invalid, and <paramref name="diagnosticOnly"/> is <c>false</c>.</exception>
+        /// <exception cref="InvalidOperationException">The represented field mask is invalid, and <paramref name="diagnosticOnly"/> is <c>false</c>.</exception>
         internal static string ToJson(IList<string> paths, bool diagnosticOnly)
         {
             var firstInvalid = paths.FirstOrDefault(p => !ValidatePath(p));
             if (firstInvalid == null)
             {
                 var writer = new StringWriter();
-                JsonFormatter.WriteString(writer, string.Join(",", paths.Select(JsonFormatter.ToCamelCase)));
+#if DOTNET35
+                var query = paths.Select(JsonFormatter.ToJsonName);
+                JsonFormatter.WriteString(writer, string.Join(",", query.ToArray()));
+#else
+                JsonFormatter.WriteString(writer, string.Join(",", paths.Select(JsonFormatter.ToJsonName)));
+#endif
                 return writer.ToString();
             }
             else
@@ -80,9 +85,9 @@ namespace Google.Protobuf.WellKnownTypes
         }
 
         /// <summary>
-        /// Camel-case converter with added strictness for field mask formatting.
+        /// Checks whether the given path is valid for a field mask.
         /// </summary>
-        /// <exception cref="InvalidOperationException">The field mask is invalid for JSON representation</exception>
+        /// <returns>true if the path is valid; false otherwise</returns>
         private static bool ValidatePath(string input)
         {
             for (int i = 0; i < input.Length; i++)