Gather histogram for received packets indicating losses.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index f411637178c9dfc7034c2ba930c04f3f6ce247da..2b49ca2905a93580cfc21429565e5d716657d246 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5728,7 +5728,7 @@ other types of suffix sets.
 
 <histogram name="Geolocation.NetworkLocationRequest.AccessPoints">
   <summary>
-    The number of wifi access points used to determine geolocation.
+    The number of WiFi access points used to determine geolocation.
   </summary>
 </histogram>
 
@@ -10228,6 +10228,22 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Net.QuicSession.PacketReceived_Ack" units="SequenceNumber">
+  <summary>
+    Each bucket contains the number of packets with a corresponding sequence
+    number that were received by the client, and hence the client ACKed the
+    packet.
+  </summary>
+</histogram>
+
+<histogram name="Net.QuicSession.PacketReceived_Nack" units="SequenceNumber">
+  <summary>
+    Each bucket contains the number of packets with a corresponding sequence
+    number were not received by the client, but for which there were later
+    packet sequence numbers received, and hence the client NACKed the packet.
+  </summary>
+</histogram>
+
 <histogram name="Net.QuicSession.PublicResetAddressMismatch"
     enum="QuicAddressMismatch">
   <summary>
@@ -12057,7 +12073,7 @@ other types of suffix sets.
 <histogram name="Network.Shill.WiFi.ApDisconnectReason" enum="WiFiReasonCode">
   <summary>
     Chrome OS network usage metric.  Reason code reported when the AP
-    disconnects a wifi connection.
+    disconnects a WiFi connection.
   </summary>
 </histogram>
 
@@ -12086,7 +12102,7 @@ other types of suffix sets.
     enum="WiFiReasonCode">
   <summary>
     Chrome OS network usage metric.  Reason code reported when the client
-    disconnects a wifi connection.
+    disconnects a WiFi connection.
   </summary>
 </histogram>
 
@@ -12221,14 +12237,14 @@ other types of suffix sets.
 
 <histogram name="Network.Shill.WiFi.ScanResult" enum="WiFiScanResult">
   <summary>
-    Chrome OS network usage metric describing, for a wifi scan attempt, what
+    Chrome OS network usage metric describing, for a WiFi scan attempt, what
     scan method is used and whether it ends in a connection.
   </summary>
 </histogram>
 
 <histogram name="Network.Shill.WiFi.ScanTimeInEbusy" units="milliseconds">
   <summary>
-    Chrome OS network usage metric describing, for a wifi scan attempt, how many
+    Chrome OS network usage metric describing, for a WiFi scan attempt, how many
     milliseconds were spent waiting to talk to the kernel/drivers.
   </summary>
 </histogram>
@@ -12464,7 +12480,7 @@ other types of suffix sets.
 
 <histogram name="Network.Wifi.RoundTripTime" units="ms">
   <summary>
-    Network metric reporting the average round trip time to the wifi gateway.
+    Network metric reporting the average round trip time to the WiFi gateway.
     Recorded at least once per day.
   </summary>
 </histogram>
@@ -34513,6 +34529,23 @@ other types of suffix sets.
   <affected-histogram name="Media.VideoCaptureManager"/>
 </fieldtrial>
 
+<fieldtrial name="Net.QuicSession.PacketReceived" separator="_">
+  <group name="CONNECTION_UNKNOWN" label="Connections via WiFi are tallied."/>
+  <group name="CONNECTION_ETHERNET"
+      label="Connections via ethernet are tallied, but this may include
+             connections to a WiFi bridge."/>
+  <group name="CONNECTION_WIFI"
+      label="Connections via WiFi are tallied, but this may include
+             connections to a mobile hotspot."/>
+  <group name="CONNECTION_2G" label="Connections via mobile 2G are tallied."/>
+  <group name="CONNECTION_3G" label="Connections via mobile 3G are tallied."/>
+  <group name="CONNECTION_4G" label="Connections via mobile 4G are tallied."/>
+  <group name="CONNECTION_NONE"
+      label="Connections via NO(?) network are tallied (should be empty)."/>
+  <affected-histogram name="Net.QuicSession.PacketReceived_Ack"/>
+  <affected-histogram name="Net.QuicSession.PacketReceived_Nack"/>
+</fieldtrial>
+
 <fieldtrial name="NetConnectivity" separator=".">
   <group name="53.100B" label="100 bytes of data on port 53."/>
   <group name="53.100B.NoProxy"