When we start up Viewer with a SampleSlide as the first slide, nothing
gets rendered because SampleSlide depends on the backend being
initialized before setting its dimensions. This pushes the first slide's
initialization after the backend creation.
Change-Id: I8f83fe7b3973c40234104f1a83c0a60750694311
Reviewed-on: https://skia-review.googlesource.com/98161
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
0848fb0b3e