As in topic. API currently offers fixed ratio only for Mac but not for Windows
shell/browser/native_window_views.cc
#if defined(OS_WIN)
  return ::GetWindowLong(GetAcceleratedWidget(), GWL_STYLE) & WS_MINIMIZEBOX;
#else
  return true;  
#endif
}
void NativeWindowViews::SetMaximizable(bool maximizable) {
#if defined(OS_WIN)
  FlipWindowStyle(GetAcceleratedWidget(), maximizable, WS_MAXIMIZEBOX);
#endif
  maximizable_ = maximizable;
}
bool NativeWindowViews::IsMaximizable() {
#if defined(OS_WIN)
  return ::GetWindowLong(GetAcceleratedWidget(), GWL_STYLE) & WS_MAXIMIZEBOX;
#else
  return true;  
#endif
}
void NativeWindowViews::SetExcludedFromShownWindowsMenu(bool excluded) {}
bool NativeWindowViews::IsExcludedFromShownWindowsMenu() {
  
  return false;
}
void NativeWindowViews::SetFullScreenable(bool fullscreenable) {
  fullscreenable_ = fullscreenable;
}
bool NativeWindowViews::IsFullScreenable() {