Expose RTT and downlink bandwidth using experimental Javascript API

third_party/WebKit/Source/modules/netinfo/NetworkInformation.cpp

Index: third_party/WebKit/Source/modules/netinfo/NetworkInformation.cpp
diff --git a/third_party/WebKit/Source/modules/netinfo/NetworkInformation.cpp b/third_party/WebKit/Source/modules/netinfo/NetworkInformation.cpp
index 02f037404613dbd4635906ccd968738681270bff..8537e8c939184da84f1336a4472005e09400d97a 100644
--- a/third_party/WebKit/Source/modules/netinfo/NetworkInformation.cpp
+++ b/third_party/WebKit/Source/modules/netinfo/NetworkInformation.cpp
@@ -40,6 +40,23 @@ String ConnectionTypeToString(WebConnectionType type) {
   return "none";
 }
 
+// Rounds |rtt_msec| to the nearest 25 milliseconds as per the NetInfo spec.
+int RoundRtt(int rtt_msec) {
+  if (rtt_msec < 0)
+    return rtt_msec;

[jkarlin, 2017/05/16 18:37:19]

This is returning a negative value but rtt() is supposed to be unsigned long
long?

[tbansal1, 2017/05/16 21:34:30]

Done.

+  return std::round(static_cast<double>(rtt_msec) / 25) * 25;
+}
+
+// Rounds |downlink_mbps| to the nearest 25 kbps as per the NetInfo spec. The
+// returned value is in Mbps.
+double RoundMbps(double downlink_mbps) {
+  if (downlink_mbps < 0)
+    return downlink_mbps;
+  double downlink_kbps = downlink_mbps * 1000;
+  double downlink_kbps_rounded = std::round(downlink_kbps / 25) * 25;
+  return downlink_kbps_rounded / 1000;
+}
+
 }  // namespace
 
 NetworkInformation* NetworkInformation::Create(ExecutionContext* context) {
@@ -67,17 +84,40 @@ double NetworkInformation::downlinkMax() const {
   return downlink_max_mbps_;
 }
 
+long NetworkInformation::rtt() const {

[jkarlin, 2017/05/16 18:37:19]

unsigned long long?

[tbansal1, 2017/05/16 21:34:30]

Done.

+  if (!observing_)
+    return RoundRtt(GetNetworkStateNotifier().TransportRttMsec());
+
+  return transport_rtt_msec_;
+}
+
+double NetworkInformation::downlink() const {
+  if (!observing_)
+    return RoundMbps(GetNetworkStateNotifier().DownlinkThroughputMbps());
+
+  return downlink_mbps_;
+}
+
 void NetworkInformation::ConnectionChange(WebConnectionType type,
-                                          double downlink_max_mbps) {
+                                          double downlink_max_mbps,
+                                          int http_rtt_msec,
+                                          int transport_rtt_msec,
+                                          double downlink_mbps) {
   DCHECK(GetExecutionContext()->IsContextThread());
 
+  transport_rtt_msec_ = RoundRtt(transport_rtt_msec);
+  downlink_mbps_ = RoundMbps(downlink_mbps);
+  // TODO(tbansal): https://crbug.com/719108. Dispatch |change| event if the
+  // expected network quality has changed.
+
   // This can happen if the observer removes and then adds itself again
-  // during notification.
+  // during notification, or if HTTP RTT was the only metric that changed.
   if (type_ == type && downlink_max_mbps_ == downlink_max_mbps)
     return;
 
   type_ = type;
   downlink_max_mbps_ = downlink_max_mbps;
+
   DispatchEvent(Event::Create(EventTypeNames::typechange));
 
   if (RuntimeEnabledFeatures::netInfoDownlinkMaxEnabled())