2 experiments: DNS prefetch limit concurrency: TCP split a packet

chrome/browser/browser_main.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/browser_main.h"
 
 #include <algorithm>
 
 #include "app/hi_res_timer_manager.h"
 #include "app/l10n_util.h"
@@ skipping 399 matching lines @@
   // Do platform-specific things (such as finishing initializing Cocoa)
   // prior to instantiating the message loop. This could be turned into a
   // broadcast notification.
   Platform::WillInitializeMainMessageLoop(parameters);
 
   MessageLoop main_message_loop(MessageLoop::TYPE_UI);
 
   SystemMonitor system_monitor;
   HighResolutionTimerManager hi_res_timer_manager;
 
-  // Initialize statistical testing infrastructure.
+  // Initialize statistical testing infrastructure for entire browser.
   FieldTrialList field_trial;
 
+  // Set up a field trial to see if splitting the first transmitted packet helps
+  // with latency.
+  {
+    FieldTrial::Probability kDivisor = 100;
+    FieldTrial* trial = new FieldTrial("PacketSplit", kDivisor);
+    // For each option (i.e., non-default), we have a fixed probability.
+    FieldTrial::Probability kProbabilityPerGroup = 10;  // 10% probability.
+    int split = trial->AppendGroup("_first_packet_split", kProbabilityPerGroup);
+    DCHECK_EQ(split, 0);
+    int intact = trial->AppendGroup("_first_packet_intact",
+                                    FieldTrial::kAllRemainingProbability);
+    DCHECK_EQ(intact, 1);
+  }
+
   std::wstring app_name = chrome::kBrowserAppName;
   std::string thread_name_string = WideToASCII(app_name + L"_BrowserMain");
 
   const char* thread_name = thread_name_string.c_str();
   PlatformThread::SetName(thread_name);
   main_message_loop.set_thread_name(thread_name);
 
   // Register the main thread by instantiating it, but don't call any methods.
   ChromeThread main_thread(ChromeThread::UI, MessageLoop::current());
 
@@ skipping 584 matching lines @@
   if (metrics)
     metrics->Stop();
 
   // browser_shutdown takes care of deleting browser_process, so we need to
   // release it.
   browser_process.release();
   browser_shutdown::Shutdown();
 
   return result_code;
 }