Only enable the refresh modes for session store cache behavior if the
currently selected mode is "Don't restore tabs until selected" to
prevent known issues with restoring too many tabs from the network
concurrently.
This resolves#1772
This resolves the situation where the device pixels per css px does not match the screen DPI.
In that case, the restored width and height would be adjusted if the window width (css px)
would be larger than the screen width (dev pixels). This patch converts everything to css px
before checking if the dimensions fit the screen.
This resolves#411.
