Reverts third_party/protobuf: Update to HEAD (f52e188fe4)

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

 #region Copyright notice and license
 // Protocol Buffers - Google's data interchange format
 // Copyright 2016 Google Inc.  All rights reserved.
 // https://developers.google.com/protocol-buffers/
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
@@ skipping 34 matching lines @@
         /// <summary>
         /// Converts a timestamp  specified in seconds/nanoseconds to a string.
         /// </summary>
         /// <remarks>
         /// If the value is a normalized duration in the range described in <c>field_mask.proto</c>,
         /// <paramref name="diagnosticOnly"/> is ignored. Otherwise, if the parameter is <c>true</c>,
         /// a JSON object with a warning is returned; if it is <c>false</c>, an <see cref="InvalidOperationException"/> is thrown.
         /// </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 field mask is invalid, and <paramref name="diagnosticOnly"/> is <c>false</c>.</exception>
+        /// <exception cref="InvalidOperationException">The represented duration 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();
-#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
+                JsonFormatter.WriteString(writer, string.Join(",", paths.Select(JsonFormatter.ToCamelCase)));
                 return writer.ToString();
             }
             else
             {
                 if (diagnosticOnly)
                 {
                     var writer = new StringWriter();
                     writer.Write("{ \"@warning\": \"Invalid FieldMask\", \"paths\": ");
                     JsonFormatter.Default.WriteList(writer, (IList)paths);
                     writer.Write(" }");
                     return writer.ToString();
                 }
                 else
                 {
                     throw new InvalidOperationException($"Invalid field mask to be converted to JSON: {firstInvalid}");
                 }
             }
         }
 
         /// <summary>
-        /// Checks whether the given path is valid for a field mask.
+        /// Camel-case converter with added strictness for field mask formatting.
         /// </summary>
-        /// <returns>true if the path is valid; false otherwise</returns>
+        /// <exception cref="InvalidOperationException">The field mask is invalid for JSON representation</exception>
         private static bool ValidatePath(string input)
         {
             for (int i = 0; i < input.Length; i++)
             {
                 char c = input[i];
                 if (c >= 'A' && c <= 'Z')
                 {
                     return false;
                 }
                 if (c == '_' && i < input.Length - 1)
@@ skipping 18 matching lines @@
         /// diagnose problems - the regular JSON formatter will still throw an exception for non-normalized
         /// values.
         /// </remarks>
         /// <returns>A string representation of this value.</returns>
         public string ToDiagnosticString()
         {
             return ToJson(Paths, true);
         }
     }
 }