shiny/screen: add width and height options to NewWindowOptions

With this change, gldriver and x11driver will parse new Width and
Height variables in NewWindowOptions. The change does not implement
parsing of the options in windriver.

Change-Id: I7c23f3b0b580ac9d4cf1d3a31b48fbc2d16046ad
Reviewed-on: https://go-review.googlesource.com/16031
Reviewed-by: Nigel Tao <nigeltao@golang.org>
3 files changed