GitLab

Since GbmBuffer moved, the only class this file defines is GbmPixmap. So
rename it.

Bug: 869206

Change-Id: If58f4590c8a118d557059368617e1521e9f16802
Reviewed-on: https://chromium-review.googlesource.com/1155920
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Maksim Sisov <msisov@igalia.com>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579822}