Make WindowTree::SetModal() take the type.

ui/aura/window_port_local.h

 // Copyright 2016 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.
 
 #ifndef UI_AURA_WINDOW_PORT_LOCAL_H_
 #define UI_AURA_WINDOW_PORT_LOCAL_H_
 
 #include "base/macros.h"
 #include "ui/aura/window_port.h"
 #include "ui/base/property_data.h"
@@ skipping 13 matching lines @@
   void OnDeviceScaleFactorChanged(float device_scale_factor) override;
   void OnWillAddChild(Window* child) override;
   void OnWillRemoveChild(Window* child) override;
   void OnWillMoveChild(size_t current_index, size_t dest_index) override;
   void OnVisibilityChanged(bool visible) override;
   void OnDidChangeBounds(const gfx::Rect& old_bounds,
                          const gfx::Rect& new_bounds) override;
   std::unique_ptr<ui::PropertyData> OnWillChangeProperty(
       const void* key) override;
   void OnPropertyChanged(const void* key,
+                         int64_t old_value,
                          std::unique_ptr<ui::PropertyData> data) override;
 
  private:
   Window* window_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowPortLocal);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_PORT_LOCAL_H_