Send a TrackedPreference incident when registry pref validation fails.

components/user_prefs/tracked/pref_hash_filter_unittest.cc

Index: components/user_prefs/tracked/pref_hash_filter_unittest.cc
diff --git a/components/user_prefs/tracked/pref_hash_filter_unittest.cc b/components/user_prefs/tracked/pref_hash_filter_unittest.cc
index fa137590bf82bbe239e9f581a0099c95ab75694c..1d3afd4b9fc3af307a2f3f7b1cf0015f417b55eb 100644
--- a/components/user_prefs/tracked/pref_hash_filter_unittest.cc
+++ b/components/user_prefs/tracked/pref_hash_filter_unittest.cc
@@ -1371,8 +1371,20 @@ TEST_P(PrefHashFilterTest, ExternalValidationValueChanged) {
   ASSERT_EQ(
       1u, mock_external_validation_pref_hash_store_->transactions_performed());
 
-  // TODO(proberge): query mock_validation_state_ for number of CHANGED
-  // and UNCHANGED preferences once the class supports external validation.
+  ASSERT_EQ(arraysize(kTestTrackedPrefs),
+            mock_validation_delegate_.recorded_validations_count());
+
+  // Regular validation should not have any CHANGED prefs.
+  ASSERT_EQ(arraysize(kTestTrackedPrefs),
+            mock_validation_delegate_.CountValidationsOfState(
+                PrefHashStoreTransaction::UNCHANGED));
+
+  // External validation should have two CHANGED prefs (kAtomic and kSplit).
+  ASSERT_EQ(2u, mock_validation_delegate_.CountExternalValidationsOfState(
+                    PrefHashStoreTransaction::CHANGED));
+  ASSERT_EQ(arraysize(kTestTrackedPrefs) - 2u,
+            mock_validation_delegate_.CountExternalValidationsOfState(
+                PrefHashStoreTransaction::UNCHANGED));
 }
 
 INSTANTIATE_TEST_CASE_P(PrefHashFilterTestInstance,