Bug 1667851 [Wayland] Use map_event to create wl_subsurface of MozContainer when it's size is already allocated, r=jhorak

- Recently we use size allocation event to create wl_subsurface of MozContainer. Unfortunately size allocation event
  is not called when a window is opened second time, as its size is already set. Use map_event to create
  wl_subsurface in this case.

Depends on D104550

Differential Revision: https://phabricator.services.mozilla.com/D104551

widget/gtk/nsWindow.cpp

@@ -1080,6 +1080,7 @@ void nsWindow::AddCSDDecorationSize(int* aWidth, int* aHeight) {
   }
 }
 
+#ifdef MOZ_WAYLAND
 bool nsWindow::GetCSDDecorationOffset(int* aDx, int* aDy) {
   if (mSizeState == nsSizeMode_Normal &&
       mCSDSupportLevel == GTK_DECORATION_CLIENT && mDrawInTitlebar) {
@@ -1091,6 +1092,7 @@ bool nsWindow::GetCSDDecorationOffset(int* aDx, int* aDy) {
     return false;
   }
 }
+#endif
 
 void nsWindow::ApplySizeConstraints(void) {
   if (mShell) {