Buffer11: Ensure we don't overflow on setData. When mapping uniform buffers for very large buffers, we could end up copying past buffer bounds. This would trigger crashes on some configs. We can fix this by clamping the copy size correctly. BUG=chromium:659892 Change-Id: I9d1af984da34867692d4c7b8908c016ebec7a63b Reviewed-on: https://chromium-review.googlesource.com/404931 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>