Remove ineffective lazy field fMetricsAndImages

In 99.99% of the cases the call to updateTextureCoordinates is only
called once per SubRun. If the regenerator was used for multiple
SubRuns, this might be interesting.

Change-Id: I95e9e526ed27dd800298711478694efef0121b66
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293563
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Herb Derby <herb@google.com>
2 files changed