Check WindowTreeClient for empty inflight queue upon teardown

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

Index: components/mus/public/cpp/tests/window_tree_client_unittest.cc
diff --git a/components/mus/public/cpp/tests/window_tree_client_unittest.cc b/components/mus/public/cpp/tests/window_tree_client_unittest.cc
index 785e766d1f623d39f2c49d3ed409ad9c98a7ed7d..5ec9eaa5bc744add5218843a8816e1c30aa19025 100644
--- a/components/mus/public/cpp/tests/window_tree_client_unittest.cc
+++ b/components/mus/public/cpp/tests/window_tree_client_unittest.cc
@@ -1037,6 +1037,9 @@ TEST_F(WindowTreeClientTest, WindowDestroyedWhileTransientChildHasCapture) {
   // 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());
 
@@ -1045,6 +1048,9 @@ TEST_F(WindowTreeClientTest, WindowDestroyedWhileTransientChildHasCapture) {
   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());
 }