Update SkPictureShader to use makeTemporaryImage()

* Update SkPictureShader image creation to use makeTemporaryImage() rather than makeImageSnapshot() to avoid any unnecessary copies.

* This is safe to do because the Surface used to generate a raster shader is fleeting (also, raster surface's impl. of makeTemporaryImage simply calls makeImageSnapshot behind the scenes anyways).

* Update the key helper to use CachedImageInfo::makeImage() rather than defining its own logic in order to avoid texture copies.

Change-Id: I6ad639da353b6a89aedb53902605856e2cd02065
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1074298
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Auto-Submit: Nicolette Prevost <nicolettep@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
3 files changed