Capture/Replay: Emit NULL instead of nullptr in trace When created C traces the value "nullptr" is not defined, so emit NULL instead, because this is supported in both, C and C++. Bug: angleproject:8018 Change-Id: I77584c462b1b02df39871929c1979d7ee7624361 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4254388 Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Cody Northrop <cnorthrop@google.com>