React to primary display change instead of removal

chrome/browser/ui/webui/chromeos/login/oobe_display_chooser_unittest.cc

Index: chrome/browser/ui/webui/chromeos/login/oobe_display_chooser_unittest.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/oobe_display_chooser_unittest.cc b/chrome/browser/ui/webui/chromeos/login/oobe_display_chooser_unittest.cc
index 517ec783ae834b9125449de84635e146ed66bfe4..acf074ae225fd6af55f93ded65c3882bc3763420 100644
--- a/chrome/browser/ui/webui/chromeos/login/oobe_display_chooser_unittest.cc
+++ b/chrome/browser/ui/webui/chromeos/login/oobe_display_chooser_unittest.cc
@@ -9,6 +9,7 @@
 #include "ash/display/display_configuration_controller.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
+#include "base/run_loop.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/display/display.h"
 #include "ui/display/display_observer.h"
@@ -63,6 +64,7 @@ TEST_F(OobeDisplayChooserTest, PreferTouchAsPrimary) {
 
   EXPECT_EQ(ids[0], GetPrimaryDisplay());
   display_chooser.TryToPlaceUiOnTouchDisplay();
+  base::RunLoop().RunUntilIdle();
 
   EXPECT_EQ(ids[1], GetPrimaryDisplay());
 }
@@ -77,6 +79,7 @@ TEST_F(OobeDisplayChooserTest, AddingSecondTouchDisplayShouldbeNOP) {
 
   EXPECT_EQ(ids[0], GetPrimaryDisplay());
   display_chooser.TryToPlaceUiOnTouchDisplay();
+  base::RunLoop().RunUntilIdle();
 
   EXPECT_EQ(ids[0], GetPrimaryDisplay());

[oshima, 2017/05/17 16:56:18]

can you add another test case where the primary display is removed?
First swap the primary display, then UpdateDisplay() with one display.

[Felix Ekblom, 2017/05/18 11:12:04]

I'm not sure I understand what this would test.

In the test environment there's no connection between DisplayObservers and
OobeDisplayChooser as that's performed by other classes in the real setup.
OobeDisplayChooser will not react to the removal of a display.

Is it possible to describe the state (DisplayManager, WindowTreeHostManager,
etc) to use for such a test statically? Or do you want me to introduce a
DisplayObserver and mimic the interaction taking place in the real setup?

[Felix Ekblom, 2017/05/22 14:40:53]

I've added a test now that trigger the bad behavior on ToT but passes with the
code in this CL. It had to be a browser test and not a unit test because for
some reason the display removal in the unit tests does not trigger the bad
state.

 }