Fix uncached getROPixels from GPU images

We were allocating a local bitmap, but then attempting to read into an
uninitialized local pixmap. The only public API that funnels the caching
hint to this function is scalePixels, so I added a test (which previously
failed).

Bug: skia:
Change-Id: Ib4370350be664935b4c85e34c70b675e6d82ba64
Reviewed-on: https://skia-review.googlesource.com/14402
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
2 files changed