Forward declare base::Time in uniformity trials.

chrome/common/metrics/variations/uniformity_field_trials.h

Index: chrome/common/metrics/variations/uniformity_field_trials.h
diff --git a/chrome/common/metrics/variations/uniformity_field_trials.h b/chrome/common/metrics/variations/uniformity_field_trials.h
index 20c152e7499413476d43bdce27d2d2cb612574ae..bd20b76570075221b7dcf90a23049ea4735917f5 100644
--- a/chrome/common/metrics/variations/uniformity_field_trials.h
+++ b/chrome/common/metrics/variations/uniformity_field_trials.h
@@ -1,18 +1,20 @@
-// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Copyright 2013 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_COMMON_METRICS_VARIATIONS_UNIFORMITY_FIELD_TRIALS_H_
 #define CHROME_COMMON_METRICS_VARIATIONS_UNIFORMITY_FIELD_TRIALS_H_
 
-#include "base/time.h"
+namespace base {
+class Time;
+}
 
 namespace chrome_variations {
 
 // 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(const base::Time& install_date);
+void SetupUniformityFieldTrials(const base::Time install_date);
 
 }  // namespace chrome_variations