Wires up WindowTreeClient::SetDisplayRoot()

ui/aura/mus/window_tree_host_mus_init_params.h

Index: ui/aura/mus/window_tree_host_mus_init_params.h
diff --git a/ui/aura/mus/window_tree_host_mus_init_params.h b/ui/aura/mus/window_tree_host_mus_init_params.h
index 0501d9b9b31041f7eacdef688a07989fce535e3e..1cc26dd253f0b89e2d18324263376d2556707862 100644
--- a/ui/aura/mus/window_tree_host_mus_init_params.h
+++ b/ui/aura/mus/window_tree_host_mus_init_params.h
@@ -13,13 +13,34 @@
 #include <vector>
 
 #include "cc/surfaces/frame_sink_id.h"
+#include "services/ui/public/interfaces/window_manager_constants.mojom.h"
 #include "ui/aura/aura_export.h"
 
+namespace display {
+class Display;
+}
+
 namespace aura {
 
 class WindowPortMus;
 class WindowTreeClient;
 
+// Used for a WindowTreeHost that corresponds to a Display that is manually
+// created by the window manager.
+struct AURA_EXPORT DisplayInitParams {

[Elliot Glaysher, 2017/04/24 21:23:17]

Make this a moveable type instead of something put in unique_ptr<>s?

[sky, 2017/04/24 21:27:15]

I didn't do that for two reasons:
1. I wanted to make it clear in WindowTreeHostMusInitParams that
DisplayInitParams is optional.
2. For WindowTreeHostMus I didn't want the extra weight of a by value member
that is only needed during setup.

+  DisplayInitParams();
+  ~DisplayInitParams();
+
+  // The display, if not provided then the Display identified by
+  // |WindowTreeHostMusInitParams::display_id| must be one of the Displays
+  // contained in Screen.
+  std::unique_ptr<display::Display> display;
+
+  ui::mojom::WmViewportMetrics viewport_metrics;
+
+  bool is_primary_display = false;
+};
+
 // Used to create a WindowTreeHostMus. The typical case is to use
 // CreateInitParamsForTopLevel().
 struct AURA_EXPORT WindowTreeHostMusInitParams {
@@ -40,6 +61,10 @@ struct AURA_EXPORT WindowTreeHostMusInitParams {
 
   // Id of the display the window should be created on.
   int64_t display_id = 0;
+
+  // Used when the WindowTreeHostMus corresponds to a new display manually
+  // created by the window manager.
+  std::unique_ptr<DisplayInitParams> display_init_params;
 };
 
 // Creates a WindowTreeHostMusInitParams that is used when creating a top-level