We cannot piggy-back on the `updateviewarea` event in order to update the stored sidebar state, since there're a number of cases where opening/switching the sidebar view won't fire a `updateviewarea` event.
Note that `updateviewarea` only fires when the position changes in the *viewer*, which means that it won't fire if e.g. the viewer is narrow, such that the sidebar overlays the document transparently; or when switching views, without the document position also changing.
This patch also moves the handling of `forceOpen` parameter in `PDFSidebar_switchView`, to prevent triggering back-to-back rendering and dispatching of events.
5657d082c7