Fix window size (see #10240) (rebased onto develop)



This is the same as gh-865 but rebased onto develop.

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Fix https://trac.openmicroscopy.org.uk/ome/ticket/10240, Screenshot before attached to ticket
![10240_after](https://f.cloud.github.com/assets/1022396/256149/511094d6-8c22-11e2-8cd1-1ad6d1d098d5.png)