Keep all references to kInstallDate inside components/metrics/

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"
 
 class PrefService;
 
+namespace base {
+class Time;
+}
+
 class ChromeBrowserFieldTrials {
  public:
   explicit ChromeBrowserFieldTrials(const base::CommandLine& command_line);
   ~ChromeBrowserFieldTrials();
 
   // Called by the browser main sequence to set up Field Trials for this client.
-  // |local_state| is used to extract properties like install time.
-  void SetupFieldTrials(PrefService* local_state);
+  // |local_state| is used to set browser-wide properties.
+  void SetupFieldTrials(const base::Time& install_time,
+                        PrefService* local_state);
 
  private:
   // Instantiates dynamic trials by querying their state, to ensure they get
   // reported as used.
   void InstantiateDynamicTrials();
 
   const base::CommandLine& parsed_command_line_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserFieldTrials);
 };
 
 #endif  // CHROME_BROWSER_CHROME_BROWSER_FIELD_TRIALS_H_