Create a new-installs-only uniformity trial.

chrome/browser/chrome_browser_field_trials.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROME_BROWSER_FIELD_TRIALS_H_
 #define CHROME_BROWSER_CHROME_BROWSER_FIELD_TRIALS_H_
 
 #include "base/basictypes.h"
 #include "base/command_line.h"
 #include "base/gtest_prod_util.h"
+#include "base/time.h"
 
 class ChromeBrowserFieldTrials {
  public:
   explicit ChromeBrowserFieldTrials(const CommandLine& command_line);
   ~ChromeBrowserFieldTrials();
 
   // Add an invocation of your field trial init function to this method.
-  void SetupFieldTrials();
+  // |install_time| is the time this browser was installed (or the last time
+  // prefs was reset). |install_time| is used by trials that are only created
+  // for new installs of the browser.
+  void SetupFieldTrials(const base::Time& install_time);
 
  private:
   FRIEND_TEST_ALL_PREFIXES(BrowserMainTest,
                            WarmConnectionFieldTrial_WarmestSocket);
   FRIEND_TEST_ALL_PREFIXES(BrowserMainTest, WarmConnectionFieldTrial_Random);
   FRIEND_TEST_ALL_PREFIXES(BrowserMainTest, WarmConnectionFieldTrial_Invalid);
 
   // A/B test for spdy when --use-spdy not set.
   void SpdyFieldTrial();
 
   // A/B test for warmest socket vs. most recently used socket.
   void WarmConnectionFieldTrial();
 
   // Field trial to see what disabling DNS pre-resolution does to
   // latency of page loads.
   void PredictorFieldTrial();
 
   // A field trial to see what effects launching Chrome automatically on
   // computer startup has on retention and usage of Chrome.
   void AutoLaunchChromeFieldTrial();
 
   // A collection of one-time-randomized and session-randomized field trials
   // intended to test the uniformity and correctness of the field trial control,
   // bucketing and reporting systems.
-  void SetupUniformityFieldTrials();
+  void SetupUniformityFieldTrials(const base::Time& install_date);
 
   // Disables the new tab field trial if not running in desktop mode.
   void DisableNewTabFieldTrialIfNecesssary();
 
   // Sets up the Safe Browsing interstitial redesign trial.
   void SetUpSafeBrowsingInterstitialFieldTrial();
 
   // Sets up the InfiniteCache field trial.
   void SetUpInfiniteCacheFieldTrial();
 
   // Sets up field trials for doing Cache Sensitivity Analysis.
   void SetUpCacheSensitivityAnalysisFieldTrial();
 
   // A field trial to determine the impact of using non-blocking reads for
   // TCP sockets on Windows instead of overlapped I/O.
   void WindowsOverlappedTCPReadsFieldTrial();
 
   // Instantiates dynamic trials by querying their state, to ensure they get
   // reported as used.
   void InstantiateDynamicTrials();
 
   const CommandLine& parsed_command_line_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserFieldTrials);
 };
 
 #endif  // CHROME_BROWSER_CHROME_BROWSER_FIELD_TRIALS_H_