Reenable testTBM2ForSmoke & fix clock sync error on ref build of Chrome on Mac

telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py

Index: telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py
diff --git a/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py b/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py
index fd6e6607516a2b9970f2c3099a028c1e7781ba9c..ccedeba2ad3919fae09a93a9e842f722e6d4ee2a 100644
--- a/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py
+++ b/telemetry/telemetry/internal/platform/tracing_agent/chrome_tracing_agent.py
@@ -178,11 +178,17 @@ class ChromeTracingAgent(tracing_agent.TracingAgent):
     for client in devtools_clients:
       version = client.GetChromeBranchNumber()
       break
-    if version and int(version) >= 2661:
+    logging.info('Chrome version: %s', version)
+    # Note, we aren't sure whether 2744 is the correct cut-off point which
+    # Chrome will support clock sync marker, however we verified that 2743 does
+    # not support clock sync (catapult/issues/2804) hence we use it here.
+    # On the next update of Chrome ref build, if testTBM2ForSmoke still fails,
+    # the cut-off branch number will need to be bumped up again.
+    if version and int(version) > 2743:
       self._RecordClockSyncMarkerDevTools(
           sync_id, record_controller_clock_sync_marker_callback,
           devtools_clients)
-    else:  # TODO(rnephew): Remove once chrome stable is past branch 2661.
+    else:  # TODO(rnephew): Remove once chrome stable is past branch 2743.
       self._RecordClockSyncMarkerAsyncEvent(
           sync_id, record_controller_clock_sync_marker_callback)