Capture/Replay: Don't try to serialize compressed textures. Instead we write out a simple string indicating compressed texel contents. We in the future could implement a GetCompressedTexImage API. Bug: angleproject:6176 Change-Id: I6673ec85ac94d5268b24bda4d510247a63fa97e4 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3032022 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com>