Functional revert of "Signal different dirty bit for vertex buffer change." Seems to be causing rendering regressions in the Google Maps benchmark. Likely causing other serious regressions. Original CL: https://chromium-review.googlesource.com/c/angle/angle/+/1684294 Bug: angleproject:3256 Change-Id: I41608a3ce3c3267097b4c1c0a6f7450cf8a2f48f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1709756 Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>