Add bisect-config-trying script and a few example configs.

tools/auto_bisect/configs/mac.bisect.blink_perf.cfg

Index: tools/auto_bisect/configs/mac.bisect.blink_perf.cfg
diff --git a/tools/auto_bisect/configs/mac.bisect.blink_perf.cfg b/tools/auto_bisect/configs/mac.bisect.blink_perf.cfg
new file mode 100644
index 0000000000000000000000000000000000000000..9e4e9d496da30388df8128874cfbce5fe8c623f0
--- /dev/null
+++ b/tools/auto_bisect/configs/mac.bisect.blink_perf.cfg
@@ -0,0 +1,20 @@
+# Sample config which should catch regression http://crbug.com/423337.
+# The regression is about 10% and the culprit CL is in the blink repository.
+# config is based on the one that was used for:
+# http://build.chromium.org/p/tryserver.chromium.perf/builders/mac_perf_bisect/builds/719
+
+config = {
+  'command': 'tools/perf/run_benchmark -v --browser=release blink_perf.events',
+  'good_revision': '299256',
+  'bad_revision': '299258',
+  'metric': 'EventsDispatchingInDeeplyNestedShadowTrees/EventsDispatchingInDeeplyNestedShadowTrees',
+  'repeat_count': '2',
+  'max_time_minutes': '10',
+  'truncate_percent': '25',
+  'bug_id': '423337',
+  'gs_bucket': 'chrome-perf',
+  'builder_host': 'master4.golo.chromium.org',
+  'builder_port': '8341',
+}
+
+# Workaround git try issue, see crbug.com/257689