Forward declare base::Time in uniformity trials.

chrome/common/metrics/variations/uniformity_field_trials.cc

Index: chrome/common/metrics/variations/uniformity_field_trials.cc
diff --git a/chrome/common/metrics/variations/uniformity_field_trials.cc b/chrome/common/metrics/variations/uniformity_field_trials.cc
index 600a727b688ddb4d992255e102ab20d18728f564..f2087944aaa93dc33476f59db9b1873bb7092985 100644
--- a/chrome/common/metrics/variations/uniformity_field_trials.cc
+++ b/chrome/common/metrics/variations/uniformity_field_trials.cc
@@ -6,6 +6,7 @@
 
 #include "base/metrics/field_trial.h"
 #include "base/stringprintf.h"
+#include "base/time.h"
 #include "chrome/common/metrics/variations/variations_util.h"
 
 namespace {
@@ -69,7 +70,7 @@ void SetupSingleUniformityFieldTrial(
 
 // Setup a 50% uniformity trial for new installs only. This is accomplished by
 // disabling the trial on clients that were installed before a specified date.
-void SetupNewInstallUniformityTrial(const base::Time& install_date) {
+void SetupNewInstallUniformityTrial(const base::Time install_date) {
   const base::Time::Exploded kStartDate = {
     2012, 11, 0, 6,  // Nov 6, 2012
     0, 0, 0, 0       // 00:00:00.000
@@ -92,7 +93,7 @@ void SetupNewInstallUniformityTrial(const base::Time& install_date) {
 
 namespace chrome_variations {
 
-void SetupUniformityFieldTrials(const base::Time& install_date) {
+void SetupUniformityFieldTrials(const base::Time install_date) {
   // One field trial will be created for each entry in this array. The i'th
   // field trial will have |trial_sizes[i]| groups in it, including the default
   // group. Each group will have a probability of 1/|trial_sizes[i]|.