Have WindowTreeClient detect error state earlier

ui/views/controls/native/native_view_host_aura_unittest.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/controls/native/native_view_host_aura.h"
 
 #include <memory>
 
 #include "base/macros.h"
 #include "ui/aura/client/aura_constants.h"
@@ skipping 87 matching lines @@
 
   void CreateHost() {
     CreateTopLevel();
     CreateTestingHost();
     child_.reset(CreateChildForHost(toplevel()->GetNativeView(),
                                     toplevel()->GetRootView(),
                                     new View,
                                     host()));
   }
 
+  // test::NativeViewHostTestBase:
+  void TearDown() override {
+    child_.reset();
+    test::NativeViewHostTestBase::TearDown();
+  }
+
  private:
   std::unique_ptr<Widget> child_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeViewHostAuraTest);
 };
 
 // Verifies NativeViewHostAura stops observing native view on destruction.
 TEST_F(NativeViewHostAuraTest, StopObservingNativeViewOnDestruct) {
   CreateHost();
   aura::Window* child_win = child()->GetNativeView();
@@ skipping 252 matching lines @@
 
   host()->SetVisible(false);
   EXPECT_FALSE(clipping_window()->IsVisible());
   EXPECT_FALSE(child()->IsVisible());
 
   DestroyHost();
   DestroyTopLevel();
 }
 
 }  // namespace views