simplify gm matrices

rm gm that appears to have been there solely for pdf, but we don't use
it for that now.

Bug: skia:
Change-Id: I3cf88db923c2445b7c95dda14da679a594117643
Reviewed-on: https://skia-review.googlesource.com/31760
Reviewed-by: Derek Sollenberger <djsollen@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
6 files changed