[metal] Fix padded LCD conversion.

In Metal on Mac, 565 is not available so we need to convert to RGBA8.
However, if we pad the glyph for bilerp and do this conversion we were
not stepping the correct amount for each row, leading to distortion.

Bug: skia:13747
Change-Id: I1554811bb7a781e0b4d5391d5f7c624c50994c3b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/584919
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Herb Derby <herb@google.com>
1 file changed