Mark a context as shared if using global textures/semaphores The display level texture/semaphore sharing allows cross-sharegroup sharing of resources. This is not thread safe without marking the context as shared which triggers locks on GL calls. Bug: chromium:1273651 Bug: chromium:1276527 Bug: chromium:1276563 Bug: chromium:1278174 Bug: chromium:1284879 Change-Id: If5214ccfd8452beb5e3079ab38c6a3f7d7225d7f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3399249 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: vikas soni <vikassoni@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>