D3D: Fix static promotion of dynamic index data. The static promotion somehow slipped into the direct usage check, meaning we would never promote dynamic index data to static, even if unchanged for many frames. Fix this by putting the update back in the correct place. BUG=angleproject:1334 Change-Id: I90897fcd2f6a2b231ccef9f1fa044d276b238b56 Reviewed-on: https://chromium-review.googlesource.com/331388 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>