When copying from a staging buffer to a uniform buffer, the first
upload would be incorrect. Work around this by trying to upload
directly to a uniform buffer on the first BufferSubData call.

BUG=chromium:593024

Change-Id: I0df3a1422b962bf3ece5d445f435df01e3544b67
Reviewed-on: https://chromium-review.googlesource.com/368774Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>