[Invalidations] Require there to be no registered handlers on Invalidator destruction

chrome/browser/signin/signin_tracker_unittest.cc

Index: chrome/browser/signin/signin_tracker_unittest.cc
diff --git a/chrome/browser/signin/signin_tracker_unittest.cc b/chrome/browser/signin/signin_tracker_unittest.cc
index 194fc030591bbf54c40f088ab8805d3594d364d8..307e85855c5de00be9591755013a8333faabe112 100644
--- a/chrome/browser/signin/signin_tracker_unittest.cc
+++ b/chrome/browser/signin/signin_tracker_unittest.cc
@@ -61,6 +61,7 @@ class SigninTrackerTest : public testing::Test {
         ProfileSyncServiceFactory::GetInstance()->SetTestingFactoryAndUse(
             profile_.get(),
             ProfileSyncServiceMock::BuildMockProfileSyncService));
+    mock_pss_->Initialize();
     // Make gmock not spam the output with information about these uninteresting
     // calls.
     EXPECT_CALL(*mock_pss_, AddObserver(_)).Times(AnyNumber());