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

This reverts commit 4b40a1d5bf0a4860099ec8c8b495466826cd2a4c.

Reason for revert: Breaking iOS/GL

Original change's description:
> 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>

TBR=egdaniel@google.com,bsalomon@google.com

Change-Id: I7f22151aad7fefd6896a57d4448d03fd3bdec0e2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:981254
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/226556
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
4 files changed