Makes a couple of tests reset state appropriately

chrome/browser/sync/sync_error_notifier_ash_unittest.cc

Index: chrome/browser/sync/sync_error_notifier_ash_unittest.cc
diff --git a/chrome/browser/sync/sync_error_notifier_ash_unittest.cc b/chrome/browser/sync/sync_error_notifier_ash_unittest.cc
index 8215226ea0b5f3ff734bc37214476664fe38a8df..8de7117f978b8907f7ef49111539992f3cde5f7e 100644
--- a/chrome/browser/sync/sync_error_notifier_ash_unittest.cc
+++ b/chrome/browser/sync/sync_error_notifier_ash_unittest.cc
@@ -108,7 +108,7 @@ class SyncErrorNotifierTest : public AshTestBase  {
 #if defined(OS_WIN)
     test_screen_.reset(aura::TestScreen::Create(gfx::Size()));
     gfx::Screen::SetScreenInstance(gfx::SCREEN_TYPE_NATIVE, test_screen_.get());
-    gfx::Screen::SetScreenTypeDelegate(new ScreenTypeDelegateDesktop);
+    gfx::Screen::SetScreenTypeDelegate(&screen_type_delegate_);
 #endif
 
     service_.reset(new NiceMock<ProfileSyncServiceMock>(profile_));
@@ -129,6 +129,8 @@ class SyncErrorNotifierTest : public AshTestBase  {
     error_notifier_->Shutdown();
     service_.reset();
 #if defined(OS_WIN)
+    gfx::Screen::SetScreenInstance(gfx::SCREEN_TYPE_NATIVE, nullptr);
+    gfx::Screen::SetScreenTypeDelegate(nullptr);
     test_screen_.reset();
 #endif
     profile_manager_.reset();
@@ -166,6 +168,7 @@ class SyncErrorNotifierTest : public AshTestBase  {
   }
 
 #if defined(OS_WIN)
+  ScreenTypeDelegateDesktop screen_type_delegate_;
   scoped_ptr<gfx::Screen> test_screen_;
 #endif
   scoped_ptr<TestingProfileManager> profile_manager_;