gm: add --ignoreTests flag

gm/tests/run.sh

 #!/bin/bash
 
 # Self-tests for gm, based on tools/tests/run.sh
 #
 # These tests are run by the Skia_PerCommit_House_Keeping bot at every commit,
 # so make sure that they still pass when you make changes to gm!
 #
 # To generate new baselines when gm behavior changes, run gm/tests/rebaseline.sh
 #
 # TODO: because this is written as a shell script (instead of, say, Python)
@@ skipping 183 matching lines @@
 gm_test "--verbose --hierarchy --match selftest1 $CONFIGS -r $GM_INPUTS/json/identical-bytes.json" "$GM_OUTPUTS/compared-against-identical-bytes-json"
 
 # Compare generated image against an input image file with identical pixels but different PNG encoding.
 gm_test "--verbose --hierarchy --match selftest1 $CONFIGS -r $GM_INPUTS/images/identical-pixels" "$GM_OUTPUTS/compared-against-identical-pixels-images"
 gm_test "--verbose --hierarchy --match selftest1 $CONFIGS -r $GM_INPUTS/json/identical-pixels.json" "$GM_OUTPUTS/compared-against-identical-pixels-json"
 
 # Compare generated image against an input image file with different pixels.
 gm_test "--verbose --hierarchy --match selftest1 $CONFIGS -r $GM_INPUTS/images/different-pixels" "$GM_OUTPUTS/compared-against-different-pixels-images"
 gm_test "--verbose --hierarchy --match selftest1 $CONFIGS -r $GM_INPUTS/json/different-pixels.json" "$GM_OUTPUTS/compared-against-different-pixels-json"
 
+# Exercise --ignoreTests flag.
+gm_test "--verbose --hierarchy --match selftest1 --ignoreTests selftest1 $CONFIGS -r $GM_INPUTS/json/different-pixels.json" "$GM_OUTPUTS/ignoring-one-test"
+
 # Compare different pixels, but with a SUBSET of the expectations marked as
 # ignore-failure.
 gm_test "--verbose --hierarchy --match selftest1 $CONFIGS -r $GM_INPUTS/json/different-pixels-ignore-some-failures.json" "$GM_OUTPUTS/ignoring-some-failures"
 
 # Compare generated image against an empty "expected image" dir.
 gm_test "--verbose --hierarchy --match selftest1 $CONFIGS -r $GM_INPUTS/images/empty-dir" "$GM_OUTPUTS/compared-against-empty-dir"
 
 # Compare generated image against a nonexistent "expected image" dir.
 gm_test "--verbose --hierarchy --match selftest1 $CONFIGS -r ../path/to/nowhere" "$GM_OUTPUTS/compared-against-nonexistent-dir"
 
@@ skipping 32 matching lines @@
 for CASE in $FAILING_CASES; do
   assert_fails "python gm/display_json_results.py $GM_OUTPUTS/$CASE/$OUTPUT_EXPECTED_SUBDIR/json-summary.txt"
 done
 
 if [ $ENCOUNTERED_ANY_ERRORS == 0 ]; then
   echo "All tests passed."
   exit 0
 else
   exit 1
 fi