Fix problem where field trials using kExpirationYearInFuture could get disabled.

The issue was that kExpirationYearInFuture was using system time, but the
expiration check in field_trial.cc was using build time. This CL changes
the constant to be named kExpirationYearNotExpired and sets it based on
build time.

BUG=168799
TEST=New unit test.

Review URL: https://chromiumcodereview.appspot.com/11783033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175831 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 20 insertions, 7 deletions

diff --git a/base/metrics/field_trial.cc b/base/metrics/field_trial.cc
index 14e16ea..66421da2 100644
--- a/base/metrics/field_trial.cc
+++ b/base/metrics/field_trial.cc
@@ -49,7 +49,7 @@ const int FieldTrial::kDefaultGroupNumber = 0;
 bool FieldTrial::enable_benchmarking_ = false;
 
 const char FieldTrialList::kPersistentStringSeparator('/');
-int FieldTrialList::kExpirationYearInFuture = 0;
+int FieldTrialList::kNoExpirationYear = 0;
 
 //------------------------------------------------------------------------------
 // FieldTrial methods and members.
@@ -244,11 +244,10 @@ FieldTrialList::FieldTrialList(
   DCHECK(!used_without_global_);
   global_ = this;
 
+  Time two_years_from_build_time = GetBuildTime() + TimeDelta::FromDays(730);
   Time::Exploded exploded;
-  Time two_years_from_now =
-      Time::NowFromSystemTime() + TimeDelta::FromDays(730);
-  two_years_from_now.LocalExplode(&exploded);
-  kExpirationYearInFuture = exploded.year;
+  two_years_from_build_time.LocalExplode(&exploded);
+  kNoExpirationYear = exploded.year;
 }
 
 FieldTrialList::~FieldTrialList() {
diff --git a/base/metrics/field_trial.h b/base/metrics/field_trial.h
index 007c1da..80f4601 100644
--- a/base/metrics/field_trial.h
+++ b/base/metrics/field_trial.h
@@ -283,8 +283,9 @@ class BASE_EXPORT FieldTrialList {
   // second process to mimic our state (i.e., provide the same group name).
   static const char kPersistentStringSeparator;  // Currently a slash.
 
-  // Define expiration year in future. It is initialized to two years from Now.
-  static int kExpirationYearInFuture;
+  // Year that is guaranteed to not be expired when instantiating a field trial
+  // via |FactoryGetFieldTrial()|.  Set to two years from the build date.
+  static int kNoExpirationYear;
 
   // Observer is notified when a FieldTrial's group is selected.
   class BASE_EXPORT Observer {
diff --git a/base/metrics/field_trial_unittest.cc b/base/metrics/field_trial_unittest.cc
index eed5f78..09a3809 100644
--- a/base/metrics/field_trial_unittest.cc
+++ b/base/metrics/field_trial_unittest.cc
@@ -717,5 +717,18 @@ TEST_F(FieldTrialTest, DisabledTrialNotActive) {
   EXPECT_TRUE(states.empty());
 }
 
+TEST_F(FieldTrialTest, ExpirationYearNotExpired) {
+  const char kTrialName[] = "NotExpired";
+  const char kGroupName[] = "Group2";
+  const int kProbability = 100;
+  ASSERT_FALSE(FieldTrialList::TrialExists(kTrialName));
+
+  FieldTrial* trial =
+      FieldTrialList::FactoryGetFieldTrial(
+          kTrialName, kProbability, kDefaultGroupName,
+          FieldTrialList::kNoExpirationYear, 1, 1, NULL);
+  trial->AppendGroup(kGroupName, kProbability);
+  EXPECT_EQ(kGroupName, trial->group_name());
+}
 
 }  // namespace base