[Sync] Removed a DCHECK in SigninInvestigator for a valid scenario.

components/signin/core/browser/signin_investigator_unittest.cc

Index: components/signin/core/browser/signin_investigator_unittest.cc
diff --git a/components/signin/core/browser/signin_investigator_unittest.cc b/components/signin/core/browser/signin_investigator_unittest.cc
index 0f5d25fff90968dfb61eea0e43a65bef64b977fd..c031865167a622f8a6af30c68f22f8c52ddb28a5 100644
--- a/components/signin/core/browser/signin_investigator_unittest.cc
+++ b/components/signin/core/browser/signin_investigator_unittest.cc
@@ -42,10 +42,16 @@ class SigninInvestigatorTest : public testing::Test {
                              const std::string& id,
                              bool equals_expectated,
                              AccountEquality histogram_expected) {
-    base::HistogramTester histogram_tester;
     FakeProvider provider(email, id);
     SigninInvestigator investigator(kSameEmail, kSameId, &provider);
-    bool equals_actual = investigator.AreAccountsEqualWithFallback();
+    AssertAccountEquality(&investigator, equals_expectated, histogram_expected);
+  }
+
+  void AssertAccountEquality(SigninInvestigator* investigator,
+                             bool equals_expectated,
+                             AccountEquality histogram_expected) {
+    base::HistogramTester histogram_tester;
+    bool equals_actual = investigator->AreAccountsEqualWithFallback();
     ASSERT_EQ(equals_expectated, equals_actual);
     histogram_tester.ExpectUniqueSample(
         "Signin.AccountEquality", static_cast<int>(histogram_expected), 1);
@@ -93,6 +99,18 @@ TEST_F(SigninInvestigatorTest, EqualityDifferentEmailFallback) {
                         AccountEquality::EMAIL_FALLBACK);
 }
 
+TEST_F(SigninInvestigatorTest, EqualitySameEmailFallbackEmptyCurrentId) {
+  FakeProvider provider(kSameEmail, kDifferentId);
+  SigninInvestigator investigator(kSameEmail, kEmptyId, &provider);
+  AssertAccountEquality(&investigator, true, AccountEquality::EMAIL_FALLBACK);
+}
+
+TEST_F(SigninInvestigatorTest, EqualityDifferentEmailFallbackEmptyCurrentId) {
+  FakeProvider provider(kDifferentId, kDifferentId);
+  SigninInvestigator investigator(kSameEmail, kEmptyId, &provider);
+  AssertAccountEquality(&investigator, false, AccountEquality::EMAIL_FALLBACK);
+}
+
 TEST_F(SigninInvestigatorTest, InvestigateSameAccount) {
   AssertInvestigatedScenario(kSameEmail, kSameId,
                              InvestigatedScenario::SAME_ACCOUNT);