Adding comments and removing optional parameter

src/VisualStudio/Core/Def/Implementation/LanguageService/AbstractPackage`2.cs

@@ -29,6 +29,7 @@ protected AbstractPackage()
         protected override void Initialize()
         {
             base.Initialize();
+            // Assume that we are being initialized on the UI thread at this point.
             var defaultForegroundThreadData = ForegroundThreadData.CreateDefault(defaultKind: ForcedByPackageInitialize);
             ForegroundThreadAffinitizedObject.CurrentForegroundThreadData = defaultForegroundThreadData;
             _foregroundObject = new ForegroundThreadAffinitizedObject(defaultForegroundThreadData);

src/VisualStudio/Core/Def/RoslynPackage.cs

@@ -44,6 +44,7 @@ protected override void Initialize()
         {
             base.Initialize();
 
+            // Assume that we are being initialized on the UI thread at this point.
             ForegroundThreadAffinitizedObject.CurrentForegroundThreadData = ForegroundThreadData.CreateDefault(defaultKind: ForcedByPackageInitialize);
             Debug.Assert(ForegroundThreadAffinitizedObject.CurrentForegroundThreadData.Kind != Unknown);
 

src/Workspaces/Core/Portable/Utilities/ForegroundThreadDataKind.cs

@@ -26,10 +26,10 @@ internal static class ForegroundThreadDataInfo
 
         static ForegroundThreadDataInfo()
         {
-            s_fallbackForegroundThreadDataKind = CreateDefault();
+            s_fallbackForegroundThreadDataKind = CreateDefault(Unknown);
         }
 
-        internal static ForegroundThreadDataKind CreateDefault(ForegroundThreadDataKind defaultKind = Unknown)
+        internal static ForegroundThreadDataKind CreateDefault(ForegroundThreadDataKind defaultKind)
         {
             var syncConextTypeName = SynchronizationContext.Current?.GetType().FullName;