Fix calculating min/max size in frameless views

The minimum and maximum size that frameless windows had used, was
incorrect. It included the border, so when it was called it actually
added that to the size, so window increased in size. The fix makes sure
that the view will use the frameless size.

This fixes #2945 and partially fixes #1806 (it also refers to some other
issues with hidpi which might still exist).

atom/browser/native_window_views.h

@@ -94,6 +94,8 @@ class NativeWindowViews : public NativeWindow,
 
   gfx::AcceleratedWidget GetAcceleratedWidget();
 
+  gfx::Size WindowSizeToFramelessSize(const gfx::Size& size);
+
   views::Widget* widget() const { return window_.get(); }
 
 #if defined(OS_WIN)