Fixes bug in ServerWindowCompositorFrameSinkManager

services/ui/ws/server_window.h

Index: services/ui/ws/server_window.h
diff --git a/services/ui/ws/server_window.h b/services/ui/ws/server_window.h
index 9dca09a4020087b2ddd58fdedd57b3e16385b679..32a4957cc09dd382e2b03415333f03a76bada415 100644
--- a/services/ui/ws/server_window.h
+++ b/services/ui/ws/server_window.h
@@ -106,6 +106,8 @@ class ServerWindow {
   const ServerWindow* parent() const { return parent_; }
   ServerWindow* parent() { return parent_; }
 
+  // NOTE: this returns null if the window does not have an ancestor associated
+  // with a display.
   const ServerWindow* GetRoot() const;
   ServerWindow* GetRoot() {
     return const_cast<ServerWindow*>(
@@ -206,6 +208,10 @@ class ServerWindow {
   // Implementation of removing a window. Doesn't send any notification.
   void RemoveImpl(ServerWindow* window);
 
+  // Called when the root window changes from |old_root| to |new_root|. This is
+  // called after the window is moved from |old_root| to |new_root|.
+  void ProcessRootChanged(ServerWindow* old_root, ServerWindow* new_root);
+
   // Called when this window's stacking order among its siblings is changed.
   void OnStackingChanged();