Added a function to BrowserMainParts that sets up field trials. It is called after about_flags has converted the flags to command-line switches. This fixes the case where a field trial would opt a user out of a feature even when they'd explicitly enabled it in their flags.

Contributed by: dominich@chromium.org

BUG=none
TEST=Enable page-prerender through about:flags and restart. You should skip the random part of the Field Test.

Review URL: http://codereview.chromium.org/6354023

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72689 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 18 insertions, 10 deletions

diff --git a/chrome/browser/browser_main.cc b/chrome/browser/browser_main.cc
index cb05347..df290e3 100644
--- a/chrome/browser/browser_main.cc
+++ b/chrome/browser/browser_main.cc
@@ -195,14 +195,6 @@ void BrowserMainParts::EarlyInitialization() {
   if (parsed_command_line().HasSwitch(switches::kEnableBenchmarking))
     base::FieldTrial::EnableBenchmarking();
 
-  // Note: make sure to call ConnectionFieldTrial() before
-  // ProxyConnectionsFieldTrial().
-  ConnectionFieldTrial();
-  SocketTimeoutFieldTrial();
-  ProxyConnectionsFieldTrial();
-  SpdyFieldTrial();
-  PrefetchFieldTrial();
-  ConnectBackupJobsFieldTrial();
   InitializeSSL();
 
   if (parsed_command_line().HasSwitch(switches::kEnableDNSSECCerts))
@@ -225,6 +217,18 @@ void BrowserMainParts::EarlyInitialization() {
   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
@@ -1251,6 +1255,10 @@ int BrowserMain(const MainFunctionParams& parameters) {
   about_flags::ConvertFlagsToSwitches(local_state,
                                       CommandLine::ForCurrentProcess());
 
+  // Now the command line has been mutated based on about:flags, we can run some
+  // field trials
+  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.
@@ -1398,8 +1406,6 @@ int BrowserMain(const MainFunctionParams& parameters) {
   }
 #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;
diff --git a/chrome/browser/browser_main.h b/chrome/browser/browser_main.h
index 7fd7142..a8f5442 100644
--- a/chrome/browser/browser_main.h
+++ b/chrome/browser/browser_main.h
@@ -80,6 +80,8 @@ class BrowserMainParts {
   void EarlyInitialization();
   void MainMessageLoopStart();
 
+  void SetupFieldTrials();
+
  protected:
   explicit BrowserMainParts(const MainFunctionParams& parameters);