Added a function to BrowserMainParts that is called after about_flags has con...

chrome/browser/browser_main.cc

 // Copyright (c) 2011 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 <string>
 #include <vector>
 
@@ skipping 175 matching lines @@
 
 BrowserMainParts::~BrowserMainParts() {
 }
 
 // BrowserMainParts: |EarlyInitialization()| and related -----------------------
 
 void BrowserMainParts::EarlyInitialization() {
   PreEarlyInitialization();
 
   if (parsed_command_line().HasSwitch(switches::kEnableBenchmarking))
     base::FieldTrial::EnableBenchmarking();

[cbentzel, 2011/01/25 22:51:41]

Why didn't this move to SetupFieldTrials? Did it need to be called early?

[dominich, 2011/01/25 22:59:26]

My first thought was that it isn't enabled through about:flags, and while you're
right that this should be in the SetupFieldTrials() method for completeness,
there may be some field trials that need to be set up earlier. This would then
need to be called before those. I thought it safer to leave it.

 
-  // Note: make sure to call ConnectionFieldTrial() before
-  // ProxyConnectionsFieldTrial().
-  ConnectionFieldTrial();
-  SocketTimeoutFieldTrial();
-  ProxyConnectionsFieldTrial();
-  SpdyFieldTrial();
-  PrefetchFieldTrial();
-  ConnectBackupJobsFieldTrial();
   InitializeSSL();
 
   if (parsed_command_line().HasSwitch(switches::kEnableDNSSECCerts))
     net::SSLConfigService::EnableDNSSEC();
   if (parsed_command_line().HasSwitch(switches::kDisableSSLFalseStart))
     net::SSLConfigService::DisableFalseStart();
   if (parsed_command_line().HasSwitch(switches::kAllowSSLMITMProxies))
     net::SSLConfigService::AllowMITMProxies();
   // Disabled to stop people playing with it.
   // if (parsed_command_line().HasSwitch(switches::kEnableSnapStart))
   //   net::SSLConfigService::EnableSnapStart();
   if (parsed_command_line().HasSwitch(
           switches::kEnableDNSCertProvenanceChecking)) {
     net::SSLConfigService::EnableDNSCertProvenanceChecking();
   }
 
   if (parsed_command_line().HasSwitch(switches::kEnableTcpFastOpen))
     net::set_tcp_fastopen_enabled(true);
 
   PostEarlyInitialization();
 }
 
+// This will be called after the command-line has been mutated by about:flags
+void BrowserMainParts::SetupFieldTrials() {
+  // Note: make sure to call ConnectionFieldTrial() before
+  // ProxyConnectionsFieldTrial().
+  ConnectionFieldTrial();
+  SocketTimeoutFieldTrial();
+  ProxyConnectionsFieldTrial();
+  PrefetchFieldTrial();
+  SpdyFieldTrial();
+  ConnectBackupJobsFieldTrial();
+}
+
 // This is an A/B test for the maximum number of persistent connections per
 // host. Currently Chrome, Firefox, and IE8 have this value set at 6. Safari
 // uses 4, and Fasterfox (a plugin for Firefox that supposedly configures it to
 // run faster) uses 8. We would like to see how much of an effect this value has
 // on browsing. Too large a value might cause us to run into SYN flood detection
 // mechanisms.
 void BrowserMainParts::ConnectionFieldTrial() {
   const base::FieldTrial::Probability kConnectDivisor = 100;
   const base::FieldTrial::Probability kConnectProbability = 1;  // 1% prob.
 
@@ skipping 1006 matching lines @@
   scoped_refptr<HistogramSynchronizer> histogram_synchronizer(
       new HistogramSynchronizer());
 
   // Initialize the prefs of the local state.
   browser::RegisterLocalState(local_state);
 
   // Convert active labs into switches. Modifies the current command line.
   about_flags::ConvertFlagsToSwitches(local_state,
                                       CommandLine::ForCurrentProcess());
 
+  // Now the command line has been mutated based on about:flags, we can run some
+  // field trials

[Nico, 2011/01/25 22:58:07]

Nit "." at end of comment

+  parts->SetupFieldTrials();
+
   // Now that all preferences have been registered, set the install date
   // for the uninstall metrics if this is our first run. This only actually
   // gets used if the user has metrics reporting enabled at uninstall time.
   int64 install_date =
       local_state->GetInt64(prefs::kUninstallMetricsInstallDate);
   if (install_date == 0) {
     local_state->SetInt64(prefs::kUninstallMetricsInstallDate,
                           base::Time::Now().ToTimeT());
   }
 
@@ skipping 127 matching lines @@
     std::string username =
         parsed_command_line.GetSwitchValueASCII(switches::kLoginUser);
     VLOG(1) << "Relaunching browser for user: " << username;
     chromeos::UserManager::Get()->UserLoggedIn(username);
 
     // Redirects Chrome logging to the user data dir.
     logging::RedirectChromeLogging(parsed_command_line);
   }
 #endif
 
-  // Modifies the current command line based on active experiments on
-  // about:flags.
   Profile* profile = CreateProfile(parameters, user_data_dir);
   if (!profile)
     return ResultCodes::NORMAL_EXIT;
 
   // Post-profile init ---------------------------------------------------------
 
   PrefService* user_prefs = profile->GetPrefs();
   DCHECK(user_prefs);
 
   // Tests should be able to tune login manager before showing it.
@@ skipping 366 matching lines @@
 #if defined(OS_CHROMEOS)
   // To be precise, logout (browser shutdown) is not yet done, but the
   // remaining work is negligible, hence we say LogoutDone here.
   chromeos::BootTimesLoader::Get()->AddLogoutTimeMarker("LogoutDone",
                                                         false);
   chromeos::BootTimesLoader::Get()->WriteLogoutTimes();
 #endif
   TRACE_EVENT_END("BrowserMain", 0, 0);
   return result_code;
 }