Add UMA Histogram for FieldTrial for Async Socket SlowStart...

net/http/http_network_transaction.cc

Index: net/http/http_network_transaction.cc
===================================================================
--- net/http/http_network_transaction.cc	(revision 24217)
+++ net/http/http_network_transaction.cc	(working copy)
@@ -1249,13 +1249,26 @@
         100);
   }
 
-  if (!reused_socket_)
+  if (!reused_socket_) {
     UMA_HISTOGRAM_CLIPPED_TIMES(
         "Net.Transaction_Connected_New",
         total_duration,
         base::TimeDelta::FromMilliseconds(1), base::TimeDelta::FromMinutes(10),
         100);
 
+    // Also record for our field trial.
+    static bool use_async_tcp(FieldTrialList::Find("AsyncSlowStart") &&
+      !FieldTrialList::Find("AsyncSlowStart")->group_name().empty());
+    if (use_async_tcp) {
+      UMA_HISTOGRAM_CLIPPED_TIMES(

[jar (doing other things), 2009/08/25 15:51:00]

I'd suggest using UMA_HISTOGRAM_CUSTOM_TIMES.  The comment in histogram.h notes
that CLIPPED_TIMES is deprecated, and should not be used, as it tends to make it
harder to do statistical analysis.  When creating new histograms, please
consider using CUSTOM rather than CLIPPED.  The clipped discards some data, and
it is better to be able to discard the percentage of data yuo desire, than to
have some unknown percentage not be logged.

+        FieldTrial::MakeName("Net.Transaction_Connected_New",
+                             "AsyncSlowStart").data(),
+        total_duration,
+        base::TimeDelta::FromMilliseconds(1), base::TimeDelta::FromMinutes(10),
+        100);
+    }
+  }
+
   // Currently, non-zero priority requests are frame or sub-frame resource
   // types.  This will change when we also prioritize certain subresources like
   // css, js, etc.