Create a new-installs-only uniformity trial.

chrome/browser/chrome_browser_main.cc

 // Copyright (c) 2012 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/chrome_browser_main.h"
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
@@ skipping 557 matching lines @@
         switches::kForceFieldTrials);
     bool ret = base::FieldTrialList::CreateTrialsFromString(persistent);
     CHECK(ret) << "Invalid --" << switches::kForceFieldTrials <<
                   " list specified.";
   }
 
   chrome_variations::VariationsService* variations_service =
       browser_process_->variations_service();
   variations_service->CreateTrialsFromSeed(browser_process_->local_state());
 
-  browser_field_trials_.SetupFieldTrials();
+  const int64 install_date = local_state_->GetInt64(
+      prefs::kUninstallMetricsInstallDate);
+  // This must be called after the pref is initialized.
+  DCHECK(install_date);
+  browser_field_trials_.SetupFieldTrials(base::Time::FromTimeT(install_date));
 
   SetupPlatformFieldTrials();
 
   // Initialize FieldTrialSynchronizer system. This is a singleton and is used
   // for posting tasks via base::Bind. Its deleted when it goes out of scope.
   // Even though base::Bind does AddRef and Release, the object will not be
   // deleted after the Task is executed.
   field_trial_synchronizer_ = new FieldTrialSynchronizer();
 }
 
@@ skipping 1095 matching lines @@
     if (base::win::GetVersion() <= base::win::VERSION_XP)
       uma_name += "_XP";
 
     uma_name += "_PreRead_";
     uma_name += pre_read_percentage;
     AddPreReadHistogramTime(uma_name.c_str(), time);
   }
 #endif
 #endif
 }