Cast: report min latency back to extension

Review URL: https://codereview.chromium.org/842113004

Cr-Commit-Position: refs/heads/master@{#311522}

chrome/renderer/extensions/cast_streaming_native_handler.cc

@@ -111,6 +111,7 @@ void FromCastRtpPayloadParams(const CastRtpPayloadParams& cast_params,
                               RtpPayloadParams* ext_params) {
   ext_params->payload_type = cast_params.payload_type;
   ext_params->max_latency = cast_params.max_latency_ms;
+  ext_params->min_latency.reset(new int(cast_params.min_latency_ms));
   ext_params->codec_name = cast_params.codec_name;
   ext_params->ssrc = cast_params.ssrc;
   ext_params->feedback_ssrc = cast_params.feedback_ssrc;