Cleanup, refactor and optimize sharing renderer code.

Author: KlausLoeffelmann

src/System.Windows.Forms/PublicAPI.Shipped.txt

@@ -1,23 +1,10 @@
 #nullable enable
 [WFO5001]static System.Windows.Forms.Application.SetColorMode(System.Windows.Forms.SystemColorMode systemColorMode) -> void
 [WFO5001]System.Windows.Forms.ControlStyles.ApplyThemingImplicitly = 524288 -> System.Windows.Forms.ControlStyles
-[WFO5001]System.Windows.Forms.Form.FormBorderColorChanged -> System.EventHandler?
-[WFO5001]System.Windows.Forms.Form.FormCaptionBackColorChanged -> System.EventHandler?
-[WFO5001]System.Windows.Forms.Form.FormCaptionTextColorChanged -> System.EventHandler?
-[WFO5001]System.Windows.Forms.Form.FormCornerPreferenceChanged -> System.EventHandler?
-[WFO5001]System.Windows.Forms.FormCornerPreference
-[WFO5001]System.Windows.Forms.FormCornerPreference.Default = 0 -> System.Windows.Forms.FormCornerPreference
-[WFO5001]System.Windows.Forms.FormCornerPreference.DoNotRound = 1 -> System.Windows.Forms.FormCornerPreference
-[WFO5001]System.Windows.Forms.FormCornerPreference.Round = 2 -> System.Windows.Forms.FormCornerPreference
-[WFO5001]System.Windows.Forms.FormCornerPreference.RoundSmall = 3 -> System.Windows.Forms.FormCornerPreference
 [WFO5001]System.Windows.Forms.SystemColorMode
 [WFO5001]System.Windows.Forms.SystemColorMode.Classic = 0 -> System.Windows.Forms.SystemColorMode
 [WFO5001]System.Windows.Forms.SystemColorMode.Dark = 2 -> System.Windows.Forms.SystemColorMode
 [WFO5001]System.Windows.Forms.SystemColorMode.System = 1 -> System.Windows.Forms.SystemColorMode
-[WFO5001]virtual System.Windows.Forms.Form.OnFormBorderColorChanged(System.EventArgs! e) -> void
-[WFO5001]virtual System.Windows.Forms.Form.OnFormCaptionBackColorChanged(System.EventArgs! e) -> void
-[WFO5001]virtual System.Windows.Forms.Form.OnFormCaptionTextColorChanged(System.EventArgs! e) -> void
-[WFO5001]virtual System.Windows.Forms.Form.OnFormCornerPreferenceChanged(System.EventArgs! e) -> void
 [WFO5002]static System.Windows.Forms.TaskDialog.ShowDialogAsync(nint hwndOwner, System.Windows.Forms.TaskDialogPage! page, System.Windows.Forms.TaskDialogStartupLocation startupLocation = System.Windows.Forms.TaskDialogStartupLocation.CenterOwner) -> System.Threading.Tasks.Task<System.Windows.Forms.TaskDialogButton!>!
 [WFO5002]static System.Windows.Forms.TaskDialog.ShowDialogAsync(System.Windows.Forms.IWin32Window! owner, System.Windows.Forms.TaskDialogPage! page, System.Windows.Forms.TaskDialogStartupLocation startupLocation = System.Windows.Forms.TaskDialogStartupLocation.CenterOwner) -> System.Threading.Tasks.Task<System.Windows.Forms.TaskDialogButton!>!
 [WFO5002]static System.Windows.Forms.TaskDialog.ShowDialogAsync(System.Windows.Forms.TaskDialogPage! page, System.Windows.Forms.TaskDialogStartupLocation startupLocation = System.Windows.Forms.TaskDialogStartupLocation.CenterScreen) -> System.Threading.Tasks.Task<System.Windows.Forms.TaskDialogButton!>!

src/System.Windows.Forms/PublicAPI.Unshipped.txt

@@ -6,4 +6,8 @@ System.Windows.Forms.FormCornerPreference.RoundSmall = 3 -> System.Windows.Forms
 virtual System.Windows.Forms.Form.OnFormBorderColorChanged(System.EventArgs! e) -> void
 virtual System.Windows.Forms.Form.OnFormCaptionBackColorChanged(System.EventArgs! e) -> void
 virtual System.Windows.Forms.Form.OnFormCaptionTextColorChanged(System.EventArgs! e) -> void
-virtual System.Windows.Forms.Form.OnFormCornerPreferenceChanged(System.EventArgs! e) -> void
+virtual System.Windows.Forms.Form.OnFormCornerPreferenceChanged(System.EventArgs! e) -> void
+[WFO5001]System.Windows.Forms.Form.FormBorderColorChanged -> System.EventHandler?
+[WFO5001]System.Windows.Forms.Form.FormCaptionBackColorChanged -> System.EventHandler?
+[WFO5001]System.Windows.Forms.Form.FormCaptionTextColorChanged -> System.EventHandler?
+[WFO5001]System.Windows.Forms.Form.FormCornerPreferenceChanged -> System.EventHandler?