use new language property of compilation/parseoption to find out which type it is

src/Workspaces/CSharp/Portable/Execution/CSharpOptionsSerializationService.cs

@@ -17,11 +17,6 @@ namespace Microsoft.CodeAnalysis.CSharp.Execution
     [ExportLanguageService(typeof(IOptionsSerializationService), LanguageNames.CSharp), Shared]
     internal class CSharpOptionsSerializationService : AbstractOptionsSerializationService
     {
-        public override bool CanSerialize(object value)
-        {
-            return value is CSharpCompilationOptions || value is CSharpParseOptions;
-        }
-
         public override void WriteTo(CompilationOptions options, ObjectWriter writer, CancellationToken cancellationToken)
         {
             WriteCompilationOptionsTo(options, writer, cancellationToken);

src/Workspaces/Core/Portable/Execution/AbstractOptionsSerializationService.cs

@@ -14,8 +14,6 @@ namespace Microsoft.CodeAnalysis.Execution
 {
     internal abstract class AbstractOptionsSerializationService : IOptionsSerializationService
     {
-        public abstract bool CanSerialize(object value);
-
         public abstract void WriteTo(CompilationOptions options, ObjectWriter writer, CancellationToken cancellationToken);
         public abstract void WriteTo(ParseOptions options, ObjectWriter writer, CancellationToken cancellationToken);
         public abstract void WriteTo(OptionSet options, ObjectWriter writer, CancellationToken cancellationToken);

src/Workspaces/Core/Portable/Execution/IOptionsSerializationService.cs

@@ -12,8 +12,6 @@ namespace Microsoft.CodeAnalysis.Execution
     /// </summary>
     internal interface IOptionsSerializationService : ILanguageService
     {
-        bool CanSerialize(object value);
-
         void WriteTo(CompilationOptions options, ObjectWriter writer, CancellationToken cancellationToken);
         void WriteTo(ParseOptions options, ObjectWriter writer, CancellationToken cancellationToken);
         void WriteTo(OptionSet options, ObjectWriter writer, CancellationToken cancellationToken);

src/Workspaces/Core/Portable/Execution/Serializer.cs

@@ -190,49 +190,6 @@ public T Deserialize<T>(string kind, ObjectReader reader, CancellationToken canc
             }
         }
 
-        private string GetLanguageName(object value)
-        {
-            // for given object, we need to figure out which language the object belong to. 
-            // we can't blindly get language service since that will bring in language specific dlls.
-            foreach (var languageName in _workspaceServices.SupportedLanguages)
-            {
-                IOptionsSerializationService service;
-                if (_lazyLanguageSerializationService.TryGetValue(languageName, out service))
-                {
-                    if (service.CanSerialize(value))
-                    {
-                        return languageName;
-                    }
-
-                    continue;
-                }
-
-                // this should be only reached once per language value actually belong to
-                var mefWorkspaceServices = _workspaceServices as MefWorkspaceServices;
-                if (mefWorkspaceServices != null)
-                {
-                    MefLanguageServices languageServices;
-                    if (!mefWorkspaceServices.TryGetLanguageServices(languageName, out languageServices))
-                    {
-                        // this is a bit fragile since it depends on implementation detail but there is no other way
-                        // to figure out which language a type belong to without loading other languages
-                        //
-                        // if a language's language services is not created yet, then it means that language is not loaded
-                        continue;
-                    }
-                }
-
-                service = GetOptionsSerializationService(languageName);
-                if (service.CanSerialize(value))
-                {
-                    return languageName;
-                }
-            }
-
-            // shouldn't reach here
-            throw ExceptionUtilities.UnexpectedValue(value);
-        }
-
         private IOptionsSerializationService GetOptionsSerializationService(string languageName)
         {
             return _lazyLanguageSerializationService.GetOrAdd(languageName, n => _workspaceServices.GetLanguageServices(n).GetService<IOptionsSerializationService>());

src/Workspaces/Core/Portable/Execution/Serializer_Asset.cs

@@ -159,9 +159,9 @@ public void SerializeCompilationOptions(CompilationOptions options, ObjectWriter
         {
             cancellationToken.ThrowIfCancellationRequested();
 
-            // TODO: once compiler team adds ability to serialize compilation options to ObjectWriter directly, we won't need this.
-            var language = GetLanguageName(options);
+            var language = options.Language;
 
+            // TODO: once compiler team adds ability to serialize compilation options to ObjectWriter directly, we won't need this.
             writer.WriteString(language);
 
             var service = GetOptionsSerializationService(language);
@@ -182,7 +182,7 @@ public void SerializeParseOptions(ParseOptions options, ObjectWriter writer, Can
         {
             cancellationToken.ThrowIfCancellationRequested();
 
-            var language = GetLanguageName(options);
+            var language = options.Language;
 
             // TODO: once compiler team adds ability to serialize parse options to ObjectWriter directly, we won't need this.
             writer.WriteString(language);

src/Workspaces/VisualBasic/Portable/Execution/VisualBasicOptionsSerializationService.vb

@@ -12,10 +12,6 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Execution
     Friend Class VisualBasicOptionsSerializationService
         Inherits AbstractOptionsSerializationService
 
-        Public Overrides Function CanSerialize(value As Object) As Boolean
-            Return (TypeOf value Is VisualBasicCompilationOptions) OrElse (TypeOf value Is VisualBasicParseOptions)
-        End Function
-
         Public Overrides Sub WriteTo(options As CompilationOptions, writer As ObjectWriter, cancellationToken As CancellationToken)
             WriteCompilationOptionsTo(options, writer, cancellationToken)