* Electron version: 1.6.5
* Operating system: macOS Sierra

If you have a window with native tab bar to the top and you open a new window, it will open as separate window. But if you are in fullscreen mode, that new window will be attached as tab. Would it make sense to have API to force a window to open into an existing tab group or not? This would make it possible to give the user the choice of wether a window should open as tab or not independent from being in fullscreen mode or not.

Not even sure such API exists on macOS though.

/cc @tonyganch
atom/browser/native_window.h
virtual void SetContentBounds(const gfx::Rect& bounds, bool animate = false);
  virtual gfx::Rect GetContentBounds();
  virtual void SetSizeConstraints(
      const extensions::SizeConstraints& size_constraints);
  virtual extensions::SizeConstraints GetSizeConstraints() const;
  virtual void SetContentSizeConstraints(
      const extensions::SizeConstraints& size_constraints);
  virtual extensions::SizeConstraints GetContentSizeConstraints() const;
  virtual void SetMinimumSize(const gfx::Size& size);
  virtual gfx::Size GetMinimumSize() const;
  virtual void SetMaximumSize(const gfx::Size& size);
  virtual gfx::Size GetMaximumSize() const;
  virtual void SetSheetOffset(const double offsetX, const double offsetY);
  virtual double GetSheetOffsetX();
  virtual double GetSheetOffsetY();
  virtual void SetResizable(bool resizable) = 0;
  virtual bool IsResizable() = 0;
  virtual void SetMovable(bool movable) = 0;
  virtual bool IsMovable() = 0;
  virtual void SetMinimizable(bool minimizable) = 0;
  virtual bool IsMinimizable() = 0;
  virtual void SetMaximizable(bool maximizable) = 0;
  virtual bool IsMaximizable() = 0;
  virtual void SetFullScreenable(bool fullscreenable) = 0;
  virtual bool IsFullScreenable() = 0;
  virtual void SetClosable(bool closable) = 0;
  virtual bool IsClosable() = 0;
  virtual void SetAlwaysOnTop(bool top,
                              const std::string& level = "floating",
                              int relativeLevel = 0,