Implement cursor changing on Mushrome

ui/display/manager/display_manager.cc

Index: ui/display/manager/display_manager.cc
diff --git a/ui/display/manager/display_manager.cc b/ui/display/manager/display_manager.cc
index 05825cacfd1db31d8e445ca7bf12abf56a68109b..51e555e6036f783c33dbd6ff19de5afc350901da 100644
--- a/ui/display/manager/display_manager.cc
+++ b/ui/display/manager/display_manager.cc
@@ -697,13 +697,13 @@ void DisplayManager::UpdateDisplaysWith(
   if (multi_display_mode_ != MIRRORING)
     multi_display_mode_ = current_default_multi_display_mode_;
 
-  CreateSoftwareMirroringDisplayInfo(&new_display_info_list);
-
   // Close the mirroring window if any here to avoid creating two compositor on
   // one display.
   if (delegate_)
     delegate_->CloseMirroringDisplayIfNotNecessary();
 
+  CreateSoftwareMirroringDisplayInfo(&new_display_info_list);

[sadrul, 2017/06/14 03:03:56]

This seems somewhat subtle. One of the ui/display owners should review this.

[Elliot Glaysher, 2017/06/15 17:35:07]

Yes, the bug here is that CloseMirroringDisplayIfNotNecessary() can access
display information. If you first call CreateSoftwareMirroringDisplayInfo(), you
get into a state where there is stale references to the current mirror display.

[oshima, 2017/06/15 18:16:17]

This was moved in this CL (https://codereview.chromium.org/1133323002), but it's
before ozone era.
I need to refresh my memory and dig code/bugs. Please give me some time.

[oshima, 2017/06/19 19:17:55]

Which reference becomes stale?

+
   Displays new_displays;
   Displays removed_displays;
   std::map<size_t, uint32_t> display_changes;