Clear GCMProfileService::account_id_ in when signing out

This fixed the bug that signing out and then signing in again does not
restart GCM.

BUG=393043
TEST=new test added

Review URL: https://codereview.chromium.org/535393002

Cr-Commit-Position: refs/heads/master@{#293319}

chrome/browser/services/gcm/gcm_profile_service.cc

@@ -111,6 +111,8 @@ void GCMProfileService::IdentityObserver::OnActiveAccountLogin() {
 }
 
 void GCMProfileService::IdentityObserver::OnActiveAccountLogout() {
+  account_id_.clear();
+
   // Check is necessary to not crash browser_tests.
   if (gcm_account_tracker_)
     gcm_account_tracker_->Stop();

chrome/browser/services/gcm/gcm_profile_service_unittest.cc

@@ -61,6 +61,7 @@ class GCMProfileServiceTest : public testing::Test {
 
   void CreateGCMProfileService();
   void SignIn();
+  void SignOut();
 
   void RegisterAndWaitForCompletion(const std::vector<std::string>& sender_ids);
   void UnregisterAndWaitForCompletion();
@@ -141,6 +142,13 @@ void GCMProfileServiceTest::SignIn() {
   base::RunLoop().RunUntilIdle();
 }
 
+void GCMProfileServiceTest::SignOut() {
+  FakeSigninManager* signin_manager = static_cast<FakeSigninManager*>(
+      SigninManagerFactory::GetInstance()->GetForProfile(profile_.get()));
+  signin_manager->SignOut(signin_metrics::SIGNOUT_TEST);
+  base::RunLoop().RunUntilIdle();
+}
+
 void GCMProfileServiceTest::RegisterAndWaitForCompletion(
     const std::vector<std::string>& sender_ids) {
   base::RunLoop run_loop;
@@ -218,6 +226,18 @@ TEST_F(GCMProfileServiceTest, CreateGCMProfileServiceAfterSignIn) {
   EXPECT_TRUE(driver()->IsStarted());
 }
 
+TEST_F(GCMProfileServiceTest, SignInAgain) {
+  CreateGCMProfileService();
+  SignIn();
+  EXPECT_TRUE(driver()->IsStarted());
+
+  SignOut();
+  EXPECT_FALSE(driver()->IsStarted());
+
+  SignIn();
+  EXPECT_TRUE(driver()->IsStarted());
+}
+
 TEST_F(GCMProfileServiceTest, RegisterAndUnregister) {
   CreateGCMProfileService();
   SignIn();