This header was not being included in every place where the macros for for the friending of test fixture were occurring. This didn't use to be a problem because base/memory/ref_counted.h used to include this header, so it would normally be pulled in transiently. Chromium change: https://chromium.googlesource.com/chromium/src/+/4b5e28be48f7b6d85f6b05d7e53bcd5591ac7665 commit 4b5e28be48f7b6d85f6b05d7e53bcd5591ac7665 Author: Daniel Cheng <dcheng@chromium.org> Date: Thu May 11 22:25:22 2023 +0000 Remove gtest_prod_util.h from //base/memory/ref_counted.h.