Updating FeatureList default initialization pattern

base/feature_list_unittest.cc

Index: base/feature_list_unittest.cc
diff --git a/base/feature_list_unittest.cc b/base/feature_list_unittest.cc
index a7e7b71183b32e7e263e4f9c7c47c382d215f56c..9d1dcb72f3094a963f71d8c889cb483b29a4a99e 100644
--- a/base/feature_list_unittest.cc
+++ b/base/feature_list_unittest.cc
@@ -457,4 +457,15 @@ TEST_F(FeatureListTest, InitializeInstance) {
   EXPECT_FALSE(FeatureList::IsEnabled(kFeatureOffByDefault));
 }
 
+TEST_F(FeatureListTest, UninitializedInstance_IsEnabledReturnsFalse) {
+  ClearFeatureListInstance();
+  // This test case simulates the calling pattern found in code which does not
+  // explicitly initialize the features list.
+  // All IsEnabled() calls should return the default value in this scenario.
+  EXPECT_EQ(nullptr, FeatureList::GetInstance());
+  EXPECT_TRUE(FeatureList::IsEnabled(kFeatureOnByDefault));
+  EXPECT_EQ(nullptr, FeatureList::GetInstance());
+  EXPECT_FALSE(FeatureList::IsEnabled(kFeatureOffByDefault));
+}
+
 }  // namespace base