Defer Sample setup to onOnceBeforeDraw.

The Atlas and BitmapRect samples do a great deal of work in their
constructors. In particular this makes setting breakpoints deep in the
glyph handling code more problematic that it needs to be, since these
will call into the glyph code when they are created which can happen
quite early. A great deal of this code does not need to run in the
constructor in any event, the work only needs to be done once before the
sample is drawn. As a result, defer this work into onOnceBeforeDraw.

Change-Id: I212d3909170bf1cb56769a45e1714f24a496472f
Reviewed-on: https://skia-review.googlesource.com/132927
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
2 files changed