Mesa: add drawable refcounting.

Backport of 122a57f86877c35904e94703d76f9022bb02b96b. This avoids
a driver-side leak which manifests in Chrome in the GPU process.

BUG=chromium:85082
TEST=Manual

Change-Id: I1a6cab758395c9400a85eeabe2867002acfc86a2
Reviewed-on: http://gerrit.chromium.org/gerrit/2946
Reviewed-by: St├ęphane Marchesin <marcheu@chromium.org>
Tested-by: David Reveman <reveman@chromium.org>
Reviewed-by: Zelidrag Hornung <zelidrag@chromium.org>
2 files changed