Reverts third_party/protobuf: Update to HEAD (f52e188fe4)

third_party/protobuf/csharp/src/Google.Protobuf/Compatibility/TypeExtensions.cs

 #region Copyright notice and license
 // Protocol Buffers - Google's data interchange format
 // Copyright 2015 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 15 matching lines @@
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endregion
 
 using System;
 using System.Reflection;
 
-#if !DOTNET35
 namespace Google.Protobuf.Compatibility
 {
     /// <summary>
     /// Provides extension methods on Type that just proxy to TypeInfo.
     /// These are used to support the new type system from .NET 4.5, without
     /// having calls to GetTypeInfo all over the place. While the methods here are meant to be
     /// broadly compatible with the desktop framework, there are some subtle differences in behaviour - but
     /// they're not expected to affect our use cases. While the class is internal, that should be fine: we can
     /// evaluate each new use appropriately.
     /// </summary>
     internal static class TypeExtensions
     {
         /// <summary>
+        /// Returns true if the target type is a value type, including a nullable value type or an enum, or false
+        /// if it's a reference type (class, delegate, interface - including System.ValueType and System.Enum).
+        /// </summary>
+        internal static bool IsValueType(this Type target)
+        {
+            return target.GetTypeInfo().IsValueType;
+        }
+
+        /// <summary>
         /// See https://msdn.microsoft.com/en-us/library/system.type.isassignablefrom
         /// </summary>
         internal static bool IsAssignableFrom(this Type target, Type c)
         {
             return target.GetTypeInfo().IsAssignableFrom(c.GetTypeInfo());
         }
 
         /// <summary>
         /// Returns a representation of the public property associated with the given name in the given type,
         /// including inherited properties or null if there is no such public property.
@@ skipping 36 matching lines @@
                 if (ret != null && ret.IsPublic)
                 {
                     return ret;
                 }
                 target = typeInfo.BaseType;
             }
             return null;
         }
     }
 }
-#endif