Inform window manager about modal windows in mus+ash.

ui/aura/mus/window_tree_client.cc

Index: ui/aura/mus/window_tree_client.cc
diff --git a/ui/aura/mus/window_tree_client.cc b/ui/aura/mus/window_tree_client.cc
index 82f54f0d6d4d97dc79c56cebfb063cc8c2b5661e..1675000ce9ed6ab3b8743dac5b5172a32e2c1d48 100644
--- a/ui/aura/mus/window_tree_client.cc
+++ b/ui/aura/mus/window_tree_client.cc
@@ -1396,6 +1396,20 @@ void WindowTreeClient::WmSetProperty(
     window_manager_internal_client_->WmResponse(change_id, result);
 }
 
+void WindowTreeClient::WmSetModalType(uint32_t change_id,
+                                      Id window_id,
+                                      ui::ModalType type) {
+  WindowMus* window = GetWindowByServerId(window_id);
+  bool result = false;
+  if (window) {
+    DCHECK(window_manager_delegate_);

[sky, 2017/03/14 21:16:23]

I think you should directly set the modal type here. I can't think of a reason
to call the delegate. IF we need to add it at some point, we can do that.

[Hadi, 2017/03/17 16:16:32]

Done.

+    result =
+        window_manager_delegate_->OnWmSetModalType(window->GetWindow(), type);
+  }
+  if (window_manager_internal_client_)
+    window_manager_internal_client_->WmResponse(change_id, result);
+}
+
 void WindowTreeClient::WmSetCanFocus(Id window_id, bool can_focus) {
   WindowMus* window = GetWindowByServerId(window_id);
   if (window)