Mojo C++ bindings: support mapping T and T? differently.

services/ui/public/cpp/tests/test_window_tree.h

 // 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.
 
 #ifndef SERVICES_UI_PUBLIC_CPP_TESTS_TEST_WINDOW_TREE_H_
 #define SERVICES_UI_PUBLIC_CPP_TESTS_TEST_WINDOW_TREE_H_
 
 #include <stdint.h>
 
 #include <set>
@@ skipping 28 matching lines @@
       uint32_t change_id,
       uint32_t window_id,
       mojo::Map<mojo::String, mojo::Array<uint8_t>> properties) override;
   void DeleteWindow(uint32_t change_id, uint32_t window_id) override;
   void SetWindowBounds(uint32_t change_id,
                        uint32_t window_id,
                        const gfx::Rect& bounds) override;
   void SetClientArea(uint32_t window_id,
                      const gfx::Insets& insets,
                      mojo::Array<gfx::Rect> additional_client_areas) override;
-  void SetHitTestMask(uint32_t window_id, const gfx::Rect& mask) override;
+  void SetHitTestMask(uint32_t window_id,
+                      const base::Optional<gfx::Rect>& mask) override;
   void SetWindowVisibility(uint32_t change_id,
                            uint32_t window_id,
                            bool visible) override;
   void SetWindowProperty(uint32_t change_id,
                          uint32_t window_id,
                          const mojo::String& name,
                          mojo::Array<uint8_t> value) override;
   void SetWindowOpacity(uint32_t change_id,
                         uint32_t window_id,
                         float opacity) override;
@@ skipping 51 matching lines @@
   uint32_t change_id_;
   std::set<uint32_t> acked_events_;
   uint32_t window_id_;
 
   DISALLOW_COPY_AND_ASSIGN(TestWindowTree);
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_PUBLIC_CPP_TESTS_TEST_WINDOW_TREE_H_