Update to CEF 88.2.9

Added the SimpleBrowser demo for Linux.
Added Linux support to TChromiumWindow.
Removed unused code and added more code comments to the SimpleBrowser demos for Windows.

demos/Lazarus_Linux/SimpleBrowser/interfaces.pas

@@ -0,0 +1,48 @@
+unit Interfaces;
+
+{$mode objfpc}{$H+}
+
+interface
+
+{$IFDEF UNIX}{$IFNDEF DisableCWString}uses cwstring;{$ENDIF}{$ENDIF}
+
+procedure CustomWidgetSetInitialization;
+procedure CustomWidgetSetFinalization;
+
+implementation
+
+uses
+ {$IFNDEF EnableLibOverlay}
+ gtk2DisableLibOverlay,
+ {$ENDIF}
+ Gtk2Int, Forms, xlib;
+
+function CustomX11ErrorHandler(Display:PDisplay; ErrorEv:PXErrorEvent):longint;cdecl;
+begin
+  {$IFDEF DEBUG}
+  XError := ErrorEv^.error_code;
+  WriteLn('Error: ' + IntToStr(XError));
+  {$ENDIF}
+  Result := 0;
+end;
+
+function CustomXIOErrorHandler(Display:PDisplay):longint;cdecl;
+begin
+  Result := 0;
+end;
+
+procedure CustomWidgetSetInitialization;
+begin
+  CreateWidgetset(TGtk2WidgetSet);
+  // Install xlib error handlers so that the application won't be terminated
+  // on non-fatal errors. Must be done after initializing GTK.
+  XSetErrorHandler(@CustomX11ErrorHandler);
+  XSetIOErrorHandler(@CustomXIOErrorHandler);
+end;
+
+procedure CustomWidgetSetFinalization;
+begin
+  FreeWidgetSet;
+end;
+
+end.