Add more out of line copy ctors for complex classes.

components/mus/ws/test_change_tracker.h

Index: components/mus/ws/test_change_tracker.h
diff --git a/components/mus/ws/test_change_tracker.h b/components/mus/ws/test_change_tracker.h
index 7f64d84020536b74f309f9adeafa353be5558f06..46103bc4c7e8333311140979c4ddc87b757def84 100644
--- a/components/mus/ws/test_change_tracker.h
+++ b/components/mus/ws/test_change_tracker.h
@@ -46,6 +46,7 @@ enum ChangeType {
 // TODO(sky): consider nuking and converting directly to WindowData.
 struct TestWindow {
   TestWindow();
+  TestWindow(const TestWindow& other);
   ~TestWindow();
 
   // Returns a string description of this.
@@ -65,6 +66,7 @@ struct TestWindow {
 // fields that are used.
 struct Change {
   Change();
+  Change(const Change& other);
   ~Change();
 
   ChangeType type;