Have WindowTreeClient detect error state earlier

ui/views/controls/native/native_view_host_aura_unittest.cc

Index: ui/views/controls/native/native_view_host_aura_unittest.cc
diff --git a/ui/views/controls/native/native_view_host_aura_unittest.cc b/ui/views/controls/native/native_view_host_aura_unittest.cc
index a0833e02a4eb74322f002c9ea60c3b1006654964..e263d29288e1e863fa48a607cdf3f8fb4f2b3dcd 100644
--- a/ui/views/controls/native/native_view_host_aura_unittest.cc
+++ b/ui/views/controls/native/native_view_host_aura_unittest.cc
@@ -105,6 +105,12 @@ class NativeViewHostAuraTest : public test::NativeViewHostTestBase {
                                     host()));
   }
 
+  // test::NativeViewHostTestBase:
+  void TearDown() override {
+    child_.reset();
+    test::NativeViewHostTestBase::TearDown();
+  }
+
  private:
   std::unique_ptr<Widget> child_;