Fix serialization.

src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo.cs

@@ -476,6 +476,7 @@ private string GetName(Node node)
         internal void AssertEquivalentTo(SymbolTreeInfo other)
         {
             Debug.Assert(_version.Equals(other._version));
+            Debug.Assert(_concatenatedNames == other._concatenatedNames);
             Debug.Assert(_nodes.Length == other._nodes.Length);
 
             for (int i = 0, n = _nodes.Length; i < n; i++)

src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo_Serialization.cs

@@ -178,6 +178,7 @@ public void WriteTo(ObjectWriter writer)
             _version.WriteTo(writer);
 
             writer.WriteString(_concatenatedNames);
+
             writer.WriteInt32(_nodes.Length);
             foreach (var node in _nodes)
             {
@@ -217,9 +218,9 @@ internal static SymbolTreeInfo ReadSymbolTreeInfo_ForTestingPurposesOnly(ObjectR
                 {
                     var version = VersionStamp.ReadFrom(reader);
 
-                    var nodeCount = reader.ReadInt32();
                     var concatenatedNames = reader.ReadString();
 
+                    var nodeCount = reader.ReadInt32();
                     var nodes = new Node[nodeCount];
                     for (var i = 0; i < nodeCount; i++)
                     {