Make cache RRect blur masks with exact fit textures.

I made this be kApprox here:
https://skia-review.googlesource.com/c/skia/+/264838

to resolve a TODO. However, it uses more memory and after thinking about
it I'm not sure why it was a TODO to use an approximate texture for a
cached texture. If it's worth caching it's probably worth making a trim
texture.

Bug: chromium:1044017

Change-Id: Iac8302291592231875f5619b33e8ee6e13a92a64
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/267444
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
2 files changed