Create a new-installs-only uniformity trial.

chrome/browser/chrome_browser_field_trials.h

Index: chrome/browser/chrome_browser_field_trials.h
diff --git a/chrome/browser/chrome_browser_field_trials.h b/chrome/browser/chrome_browser_field_trials.h
index 384621f1b45e4c96cc4bfb74c57651409eb22710..cc097a785d443d891a94e3b938895314fccfffb3 100644
--- a/chrome/browser/chrome_browser_field_trials.h
+++ b/chrome/browser/chrome_browser_field_trials.h
@@ -8,6 +8,7 @@
 #include "base/basictypes.h"
 #include "base/command_line.h"
 #include "base/gtest_prod_util.h"
+#include "base/time.h"
 
 class ChromeBrowserFieldTrials {
  public:
@@ -15,7 +16,10 @@ class ChromeBrowserFieldTrials {
   ~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,
@@ -40,7 +44,7 @@ class ChromeBrowserFieldTrials {
   // 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();