Enable HTTP pipelining field trial on dev channel for 10% of users.

chrome/browser/net/http_pipelining_compatibility_client.cc

Index: chrome/browser/net/http_pipelining_compatibility_client.cc
diff --git a/chrome/browser/net/http_pipelining_compatibility_client.cc b/chrome/browser/net/http_pipelining_compatibility_client.cc
index 5a179890f453292d5a85e83e4c3922b68cff1365..1fc294fb3750dafc2ac10ad2cff159d805b50908 100644
--- a/chrome/browser/net/http_pipelining_compatibility_client.cc
+++ b/chrome/browser/net/http_pipelining_compatibility_client.cc
@@ -475,6 +475,8 @@ void CollectPipeliningCapabilityStatsOnIOThread(
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
   if (channel == chrome::VersionInfo::CHANNEL_CANARY) {
     probability_to_run_test = 100;
+  } else if (channel == chrome::VersionInfo::CHANNEL_DEV) {
+    probability_to_run_test = 10;
   }
 
   int collect_stats_group = trial->AppendGroup("enable_test",