Plug-in view content scale support.
This interface communicates the content scale factor from the host to the plug-in view on systems where plug-ins cannot get this information directly like Microsoft Windows.
The host calls setContentScaleFactor directly after the plug view was attached and when the scale factor changes (system change or window moved to another screen with different scaling settings). The host could call setContentScaleFactor in a different context, for example: scaling the plug-in editor for better readability. When a plug-in handles this (by returning kResultTrue), it needs to scale the width and height of its view by the scale factor and inform the host via a IPlugFrame::resizeView(), the host will then call IPlugView::onSize().
Note that the host is allowed to call setContentScaleFactor() at any time the IPlugView is alive.