Remove shim files for private Chrome GPU usage

No longer needed after https://chromium-review.googlesource.com/c/chromium/src/+/4163300

Change-Id: I620bfadd96e220f25ad348be300ccd78d85aabf7
Bug: skia:13983
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/630757
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Auto-Submit: Kevin Lubick <kjlubick@google.com>
5 files changed