Bug 1677987 - Collect telemetry on the success rate of http requests with HTTP3 r=necko-reviewers,valentin

Differential Revision: https://phabricator.services.mozilla.com/D97444

netwerk/protocol/http/nsHttpChannel.cpp

@@ -7353,6 +7353,10 @@ nsHttpChannel::OnStartRequest(nsIRequest* request) {
   Telemetry::Accumulate(Telemetry::HTTP_CHANNEL_ONSTART_SUCCESS,
                         NS_SUCCEEDED(mStatus));
 
+  Telemetry::Accumulate(Telemetry::HTTP3_CHANNEL_ONSTART_SUCCESS,
+                        (mTransaction->IsHttp3Used()) ? "http3"_ns : "no_http3"_ns,
+                        NS_SUCCEEDED(mStatus));
+
   if (gTRRService && gTRRService->IsConfirmed()) {
     Telemetry::Accumulate(Telemetry::HTTP_CHANNEL_ONSTART_SUCCESS_TRR,
                           TRRService::AutoDetectedKey(), NS_SUCCEEDED(mStatus));

toolkit/components/telemetry/Histograms.json

@@ -3450,6 +3450,17 @@
     "bug_numbers": [1655566],
     "description": "HTTP3: number of times when a stream is blocked by the flow control while sendnig data."
   },
+  "HTTP3_CHANNEL_ONSTART_SUCCESS" : {
+    "record_in_processes": ["main", "content"],
+    "products": ["firefox"],
+    "expires_in_version": "never",
+    "kind": "boolean",
+    "description": "Successfully started HTTP channels when HTTP3 is used",
+    "bug_numbers": [1677987],
+    "releaseChannelCollection": "opt-out",
+    "keyed": true,
+    "alert_emails": ["necko@mozilla.com", "ddamjanovic@mozilla.com"]
+  },
   "HTTP_CONTENT_ENCODING": {
     "record_in_processes": ["main", "content"],
     "products": ["firefox", "fennec"],