Revert "Revert "Restore GL_UNPACK_ROW_LENGTH to 0 between MIP levles""

This reverts commit abb5a315af45cdfc13fbe71265e8630041f8d845.

Two fixes:
  1) GMs pass valid rowBytes when calling directly to GrGpu.
  2) Check for non-null data before trying to set UNPACK_ROW_LENGTH

Bug: chromium:981254

Change-Id: I24e46b0d2b14562d6b84a29fefe3410ce5c06c94
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/226498
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
4 files changed