Add flag to enable immersive fullscreen for v2 apps

chrome/browser/ui/gtk/apps/native_app_window_gtk.cc

Index: chrome/browser/ui/gtk/apps/native_app_window_gtk.cc
diff --git a/chrome/browser/ui/gtk/apps/native_app_window_gtk.cc b/chrome/browser/ui/gtk/apps/native_app_window_gtk.cc
index 1010390215b3b916294c56cdb4d0ac7ecfa00253..99c243c749fab42a45d56f5358c510b186dda711 100644
--- a/chrome/browser/ui/gtk/apps/native_app_window_gtk.cc
+++ b/chrome/browser/ui/gtk/apps/native_app_window_gtk.cc
@@ -454,7 +454,7 @@ void NativeAppWindowGtk::OnConfigureDebounced() {
   // Fullscreen of non-resizable windows requires them to be made resizable
   // first. After that takes effect and OnConfigure is called we transition
   // to fullscreen.
-  if (!IsFullscreen() && IsFullscreenOrPending()) {
+  if (!IsFullscreen() && content_thinks_its_fullscreen_) {
     gtk_window_fullscreen(window_);
   }
 
@@ -592,9 +592,10 @@ gboolean NativeAppWindowGtk::OnButtonPress(GtkWidget* widget,
 
 // NativeAppWindow implementation:
 
-void NativeAppWindowGtk::SetFullscreen(bool fullscreen) {
+void NativeAppWindowGtk::SetFullscreen(ShellWindow::FullscreenType type) {
+  bool fullscreen = (type != ShellWindow::FULLSCREEN_TYPE_NONE);
   content_thinks_its_fullscreen_ = fullscreen;
-  if (fullscreen){
+  if (fullscreen) {
     if (resizable_) {
       gtk_window_fullscreen(window_);
     } else {
@@ -609,13 +610,8 @@ void NativeAppWindowGtk::SetFullscreen(bool fullscreen) {
   }
 }
 
-bool NativeAppWindowGtk::IsFullscreenOrPending() const {
-  // |content_thinks_its_fullscreen_| is used when transitioning, and when
-  // the state change will not be made for some time. However, it is possible
-  // for a state update to be made before the final fullscreen state comes.
-  // In that case, |content_thinks_its_fullscreen_| will be cleared, but we
-  // will fall back to |IsFullscreen| which will soon have the correct state.
-  return content_thinks_its_fullscreen_ || IsFullscreen();
+bool NativeAppWindowGtk::SupportsImmersiveFullscreen() const {
+  return false;
 }
 
 bool NativeAppWindowGtk::IsDetached() const {