metrics: Shutdown LoginState after CrOSMetricsProvider tests

BUG=chromium:379140
TEST=unit tests pass
Signed-off-by: Simon Que <sque@chromium.org>

Review URL: https://codereview.chromium.org/302153003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@274012 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/metrics/chromeos_metrics_provider_unittest.cc

@@ -81,7 +81,12 @@ class ChromeOSMetricsProviderTest : public testing::Test {
       chromeos::LoginState::Initialize();
   }
 
-  virtual void TearDown() OVERRIDE { DBusThreadManager::Shutdown(); }
+  virtual void TearDown() OVERRIDE {
+    // Destroy the login state tracker if it was initialized.
+    chromeos::LoginState::Shutdown();
+
+    DBusThreadManager::Shutdown();
+  }
 
  protected:
   FakeBluetoothAdapterClient* fake_bluetooth_adapter_client_;