Add frameless for ShellWindow on gtk.

chrome/browser/ui/gtk/extensions/shell_window_gtk.cc

Index: chrome/browser/ui/gtk/extensions/shell_window_gtk.cc
diff --git a/chrome/browser/ui/gtk/extensions/shell_window_gtk.cc b/chrome/browser/ui/gtk/extensions/shell_window_gtk.cc
index 5359588aebf16601400cdc7c718bb0f805e4ad63..8d44025e680666d656a7badcbea74a1d35fee08c 100644
--- a/chrome/browser/ui/gtk/extensions/shell_window_gtk.cc
+++ b/chrome/browser/ui/gtk/extensions/shell_window_gtk.cc
@@ -30,6 +30,10 @@ ShellWindowGtk::ShellWindowGtk(Profile* profile,
   gtk_window_set_default_size(
       window_, params.bounds.width(), params.bounds.height());
 
+  // Hide titlebar when {frame: 'none'} on ShellWindow.
+  if (params.frame == ShellWindow::CreateParams::FRAME_NONE)
+    gtk_window_set_decorated(window_, false);
+
   int min_width = params.minimum_size.width();
   int min_height = params.minimum_size.height();
   int max_width = params.maximum_size.width();