Set SKIPPED status on skipped tests, rely on it in Gold tests. Gold tests check for '[ SKIPPED ] {test_name}' notice in test output instead of assuming that missing screenshot means SKIP. Now missing screenshot raises an exception. Also log the reason why the test was skipped. Example: [ RUN ] TracePerfTest.Run/native_asphalt_8 ../../src/tests/perf_tests/ANGLEPerfTest.cpp:837: Skipped Test skipped due to missing extension: GL_KHR_texture_compression_astc_ldr [ SKIPPED ] TracePerfTest.Run/native_asphalt_8 (182 ms) Bug: angleproject:6854 Change-Id: I2d88e2063a68ae95399a7932700f74032737ec91 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3565561 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Roman Lavrov <romanl@google.com>