As seen in bug 1757534, we apparently don't have any tests for GMP telemetry on Aarch64 builds. The patch that introduced this telemetry, bug 1745511, added a test, but it looks like we only run plain Mochitests in the dom/media directory on Aarch64 Windows, so we don't run it on this platform. The GMP telemetry exercises a unique set of code (sending ByteBuf between x86 and 64-bit processes) so it would be nice to have at least a basic test.