Rule out new skia::RefPtr objects via presubmit

Chrome is being migrated from skia::RefPtr to sk_sp<> smart pointers;
update the global presubmit script now so we don't have new instances
intruding while we chase down the last few deprecated ones.

BUG=skia:5077

Review URL: https://codereview.chromium.org/1882913002

Cr-Commit-Position: refs/heads/master@{#388275}
1 file changed