Capture/Replay: Two cleanups. This changes from returning a vector to directly returning a pointer to the binary data for the serialized state. The second cleanup is to use a ContextID as a wrapped type which simplifies the output formatting code. Bug: angleproject:5247 Change-Id: Ieb8afdb9326a12968dd2d69c05e1ed811b93abff Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2506198 Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>