Makes it so each windowtreeclient can use whatever ids it wants

components/mus/ws/window_finder.cc

 // Copyright 2015 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.
 
 #include "components/mus/ws/window_finder.h"
 
 #include "cc/surfaces/surface_id.h"
 #include "components/mus/surfaces/surfaces_state.h"
 #include "components/mus/ws/server_window.h"
 #include "components/mus/ws/server_window_delegate.h"
@@ skipping 80 matching lines @@
     // CompositorFrame has been submitted (e.g. in unit-tests).
     return FindDeepestVisibleWindowNonSurface(root_window, location);
   }
 
   gfx::Transform transform;
   cc::SurfaceId target_surface =
       root_window->delegate()
           ->GetSurfacesState()
           ->hit_tester()
           ->GetTargetSurfaceAtPoint(display_surface_id, *location, &transform);
+  // TODO(sky): this is now wrong, needs mapping from client to window.
   WindowId id = WindowIdFromTransportId(
       cc::SurfaceIdAllocator::NamespaceForId(target_surface));
   // TODO(fsamuel): This should be a DCHECK but currently we use stale
   // information to decide where to route input events. This should be fixed
   // once we implement a UI scheduler.
   ServerWindow* target = root_window->GetChildWindow(id);
   if (target)
     transform.TransformPoint(location);
   return target;
 }
 
 gfx::Transform GetTransformToWindow(cc::SurfaceId display_surface_id,
                                     ServerWindow* window) {
   if (!display_surface_id.is_null()) {
     gfx::Transform transform;
     if (HitTestSurfaceOfType(display_surface_id, window,
                              mus::mojom::SurfaceType::DEFAULT, &transform) ||
         HitTestSurfaceOfType(display_surface_id, window,
                              mus::mojom::SurfaceType::UNDERLAY, &transform)) {
       return transform;
     }
   }
 
   return GetTransformToWindowNonSurface(window);
 }
 
 }  // namespace ws
 }  // namespace mus