[Telemetry] Add API for updating ts_proxy_server's traffic settings

telemetry/telemetry/internal/util/ts_proxy_server.py

Index: telemetry/telemetry/internal/util/ts_proxy_server.py
diff --git a/telemetry/telemetry/internal/util/ts_proxy_server.py b/telemetry/telemetry/internal/util/ts_proxy_server.py
index ee72b9860d1e31a1725e3c31a869c2b669163621..abedfcc868781fd3b2a1ef857720d1b9e888568a 100644
--- a/telemetry/telemetry/internal/util/ts_proxy_server.py
+++ b/telemetry/telemetry/internal/util/ts_proxy_server.py
@@ -113,6 +113,12 @@ class TsProxyServer(object):
     self._IssueCommand('set mapports 443:%i,*:%i' % (https_port, http_port),
                        timeout)
 
+  def UpdateTrafficSettings(self, round_trip_latency_ms=0,
+      download_bandwidth_kbps=0, upload_bandwidth_kbps=0, timeout=5):
+    self._IssueCommand('set rtt %s' % round_trip_latency_ms, timeout)
+    self._IssueCommand('set inkbps %s' % download_bandwidth_kbps, timeout)
+    self._IssueCommand('set outkbps %s' % upload_bandwidth_kbps, timeout)
+
   def StopServer(self):
     """Stop TsProxy Server."""
     if not self._is_running: