Avoid OveridePaintFilterCanvas in Viewer when possible

Since:

https://skia-review.googlesource.com/c/skia/+/431539 (Feed all top-level GPU accessors through skgpu::BaseDevice (take 2))

The OveridePaintFilterCanvas now blocks access to the true SurfaceDrawContext that backs the top device of a GPU-backed SkCanvas. This is because the SkPaintFilterCanvas doesn't pass on SkCanvas::topDevice calls to the canvas it is wrapping so it always returns a SkNoPixelsDevice.

Given that accessing the top SDC is an incredibly specialized testing-only feature this CL keeps the feature working short-term w/o gumming up the public API.

Change-Id: I99012ba34c2800e0149251667156b412c4e8aa63
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/433362
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
2 files changed