Maintain window position and size when re-created

Eliminates a UI oddity on Windows when cycling through backends.

BUG=skia:

Change-Id: I83f0325054def80bb9b6e5a9886461f8aad215ae
Reviewed-on: https://skia-review.googlesource.com/9453
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
2 files changed