Check WindowTreeClient for empty inflight queue upon teardown

components/mus/public/cpp/tests/window_tree_client_unittest.cc

 // Copyright 2015 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 "components/mus/public/cpp/window_tree_client.h"
 
 #include <stdint.h>
 
 #include "base/logging.h"
 #include "base/macros.h"
@@ skipping 1019 matching lines @@
 
   transient_parent->AddTransientWindow(transient_child);
 
   WindowTracker tracker;
   tracker.Add(transient_parent);
   tracker.Add(transient_child);
   // Request a capture on the transient child, then destroy the transient
   // parent. That will destroy both windows, and should reset the capture window
   // correctly.
   transient_child->SetCapture();
+  uint32_t change_id1;
+  ASSERT_TRUE(setup.window_tree()->GetAndClearChangeId(&change_id1));
+  setup.window_tree_client()->OnChangeCompleted(change_id1, true);

[sadrul, 2016/06/15 06:42:46]

I think this adds burden to individual tests that we do not really need to
carry.

[jonross, 2016/06/15 14:03:07]

An alternate modification I considered was changing the focus/capture
InFlightChanges to include tracking the target window.

This would allow for the queued changes to be removed in
WindowTreeClient::OnWindowDestroyed

   transient_parent->Destroy();
   EXPECT_TRUE(tracker.windows().empty());
 
   // Create a new Window, and attempt to place capture on that.
   Window* child = setup.client()->NewWindow();
   child->SetVisible(true);
   root->AddChild(child);
   child->SetCapture();
+  uint32_t change_id2;
+  ASSERT_TRUE(setup.window_tree()->GetAndClearChangeId(&change_id2));
+  setup.window_tree_client()->OnChangeCompleted(change_id2, true);
   EXPECT_TRUE(child->HasCapture());
 }
 
 }  // namespace mus