Bug 1696945 - Part 2: Add Http Channel completon PerfStats r=necko-reviewers,dragana

Record from asyncOpen to channel completion in HttpChannelChild, for both network and cache sources.
This will allow us to capture cross-platform networking timings in pageload and other scenarios.

Differential Revision: https://phabricator.services.mozilla.com/D107507

netwerk/protocol/http/HttpChannelChild.cpp

@@ -11,6 +11,7 @@
 #include "nsHttp.h"
 #include "nsICacheEntry.h"
 #include "mozilla/BasePrincipal.h"
+#include "mozilla/PerfStats.h"
 #include "mozilla/Unused.h"
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/DocGroup.h"
@@ -910,6 +911,15 @@ void HttpChannelChild::OnStopRequest(
   }
 #endif
 
+  if (mIsFromCache) {
+    PerfStats::RecordMeasurement(PerfStats::Metric::HttpChannelCompletion_Cache,
+                                 TimeStamp::Now() - mAsyncOpenTime);
+  } else {
+    PerfStats::RecordMeasurement(
+        PerfStats::Metric::HttpChannelCompletion_Network,
+        TimeStamp::Now() - mAsyncOpenTime);
+  }
+
   mResponseTrailers = MakeUnique<nsHttpHeaderArray>(aResponseTrailers);
 
   DoPreOnStopRequest(aChannelStatus);