aura-mus: Implement stacking in DesktopWindowTreeHostMus.

services/ui/ws/window_tree.cc

Index: services/ui/ws/window_tree.cc
diff --git a/services/ui/ws/window_tree.cc b/services/ui/ws/window_tree.cc
index e424cf317f94becfbcf48d41513cabe789e1dcec..427b450a69a48a1bb9a127f724958fb8c1ce06d4 100644
--- a/services/ui/ws/window_tree.cc
+++ b/services/ui/ws/window_tree.cc
@@ -1605,6 +1605,39 @@ void WindowTree::DeactivateWindow(Id window_id) {
       wm_tree->ClientWindowIdForWindow(window).id);
 }
 
+void WindowTree::StackAtTop(uint32_t change_id, Id window_id) {
+  ServerWindow* window =
+      GetWindowByClientId(ClientWindowId(window_id));
+  if (!window) {
+    DVLOG(1) << "StackAtTop failed (invalid id)";
+    client()->OnChangeCompleted(change_id, false);
+    return;
+  }
+
+  ServerWindow* parent = window->parent();
+  if (!parent) {
+    DVLOG(1) << "StackAtTop failed (window unparented)";
+    client()->OnChangeCompleted(change_id, false);
+    return;
+  }
+
+  DCHECK(!parent->children().empty());
+  if (parent->children().back() == window) {
+    // Ignore this call; the client didn't know they were already at the top.
+    DVLOG(1) << "StackAtTop ignored (already at top)";

[sky, 2017/01/19 22:20:59]

As this isn't a failure (response is true), how about changing to 3. 3 better
matches similar places in this file.

[Elliot Glaysher, 2017/01/20 01:03:44]

Done.

+    client()->OnChangeCompleted(change_id, true);
+    return;
+  }
+
+  ServerWindow* relative_window = parent->children().back();

[sky, 2017/01/19 22:20:59]

Please call through to the accesspolicy. See line 1579 for an example. The
access policy should only allow this if the client doesn't own the window, but
the windowmanager does, and the implementation should redirect to the window
manager. Ash will then handle the reorder.

[Elliot Glaysher, 2017/01/20 01:03:44]

I've added an access policy check, though per discussion, it isn't forwarding to
the window manager.

+  Operation op(this, window_server_, OperationType::REORDER_WINDOW);
+  window->Reorder(relative_window, mojom::OrderDirection::ABOVE);
+  window_server_->ProcessWindowReorder(window, relative_window,
+                                       mojom::OrderDirection::ABOVE);
+
+  client()->OnChangeCompleted(change_id, true);
+}
+
 void WindowTree::GetWindowManagerClient(
     mojo::AssociatedInterfaceRequest<mojom::WindowManagerClient> internal) {
   if (!access_policy_->CanSetWindowManager() || !window_manager_internal_ ||