aura-mus: Implement DesktopWindowTreeHostMus::StackAbove().

services/ui/public/interfaces/window_tree.mojom

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module ui.mojom;
 
 import "cc/ipc/surface_info.mojom";
 import "cc/ipc/mojo_compositor_frame_sink.mojom";
 import "services/ui/public/interfaces/cursor.mojom";
 import "services/ui/public/interfaces/event_matcher.mojom";
@@ skipping 246 matching lines @@
   // accept events, none of its descendant windows accept events either.
   SetCanAcceptEvents(uint32 window_id, bool accept_events);
 
   // See documentation for WindowTreeClient::OnWindowInputEvent().
   OnWindowInputEventAck(uint32 event_id, EventResult result);
 
   // If the current focus is (or is a child of) |window_id|, requests that the
   // window manager change the focus to the next activatable window.
   DeactivateWindow(uint32 window_id);
 
+  // Stacks the window |above_id| above |below_id|. These two windows must
+  // share the same parent.
+  StackAbove(uint32 change_id, uint32 above_id, uint32 below_id);
+
   // Stacks the window above all sibling windows.
   StackAtTop(uint32 change_id, uint32 window_id);
 
   // See description of WindowManager for details.
   GetWindowManagerClient(associated WindowManagerClient& internal);
 
   // Returns a shared memory segment that contains two 16-bit ints packed into a
   // single Atomic32, which represent the current location of the mouse cursor
   // where the location is (x << 16) | y.
   GetCursorLocationMemory() => (handle<shared_buffer> cursor_buffer);
@@ skipping 218 matching lines @@
   // See description of WindowManager for details.
   GetWindowManager(associated WindowManager& internal);
 };
 
 // Mus provides this interface as a way for clients to connect and obtain a
 // WindowTree handle with a supplied WindowTreeClient handle. The
 // WindowTreeClient has no roots, use NewTopLevelWindow() to create one.
 interface WindowTreeFactory {
   CreateWindowTree(WindowTree& tree_request, WindowTreeClient client);
 };