Wires up transient windows for aura-mus

ui/aura/test/mus/test_window_tree.h

Index: ui/aura/test/mus/test_window_tree.h
diff --git a/ui/aura/test/mus/test_window_tree.h b/ui/aura/test/mus/test_window_tree.h
index d1f8b3fd9b1dc95ab1905c45508d4439fc29570a..1d96ebfa105efc18165ecd3a06059826a5f4ff3f 100644
--- a/ui/aura/test/mus/test_window_tree.h
+++ b/ui/aura/test/mus/test_window_tree.h
@@ -11,10 +11,12 @@
 
 #include "base/macros.h"
 #include "services/ui/public/interfaces/window_tree.mojom.h"
+#include "ui/aura/mus/mus_types.h"
 
 namespace aura {
 
 enum class WindowTreeChangeType {
+  ADD_TRANSIENT,
   BOUNDS,
   // Used for both set and release capture.
   CAPTURE,
@@ -22,12 +24,18 @@ enum class WindowTreeChangeType {
   NEW_TOP_LEVEL,
   NEW_WINDOW,
   PROPERTY,
+  REMOVE_TRANSIENT,
   VISIBLE,
 
   // This covers all cases that aren't used in tests.
   OTHER,
 };
 
+struct TransientData {
+  Id parent_id;
+  Id child_id;
+};
+
 // WindowTree implementation for tests. TestWindowTree maintains a list of all
 // calls that take a change_id and are expected to be acked back to the client.
 // Various functions are provided to respond to the changes.
@@ -68,6 +76,9 @@ class TestWindowTree : public ui::mojom::WindowTree {
 
   size_t GetChangeCountForType(WindowTreeChangeType type);
 
+  // Data from most recent add/remove transient window.
+  const TransientData& transient_data() const { return transient_data_; }
+
  private:
   struct Change {
     WindowTreeChangeType type;
@@ -176,6 +187,8 @@ class TestWindowTree : public ui::mojom::WindowTree {
 
   mojo::Map<mojo::String, mojo::Array<uint8_t>> last_new_window_properties_;
 
+  TransientData transient_data_;
+
   DISALLOW_COPY_AND_ASSIGN(TestWindowTree);
 };