Fix VK WritePixels with offset rect

VkUploadPixelsTest was failing because it was reallocating
the image when it didn't need to, because it was not
resetting the rowBytes when it did need to, and because the
origin was incorrect when using bottom-up images.

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1940963002

Review-Url: https://codereview.chromium.org/1940963002
1 file changed