[mus+ash] Implements hit-test client in Aura

ui/aura/mus/hit_test_data_provider_mus.h

+// Copyright 2017 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_MUS_HIT_TEST_DATA_PROVIDER_MUS_H_
+#define UI_AURA_MUS_HIT_TEST_DATA_PROVIDER_MUS_H_
+
+#include "base/macros.h"
+#include "components/viz/client/hit_test_data_provider.h"
+
+namespace aura {
+
+class Window;
+
+class HitTestDataProviderMus : public viz::HitTestDataProvider {
+ public:
+  HitTestDataProviderMus(Window* window);
+  ~HitTestDataProviderMus() override;
+
+  // HitTestDataProvider:
+  std::unique_ptr<HitTestRegionList> GetHitTestData() override;
+
+ private:
+  // Recursively walks the children of |window| and uses |window|'s
+  // EventTargeter to generate hit-test data for the |window|'s descendants.
+  // Populates |hit_test_region_list|.
+  void GetHitTestDataRecursively(aura::Window* window,
+                                 HitTestRegionList* hit_test_region_list);
+
+  aura::Window* window_ = nullptr;
+
+  DISALLOW_COPY_AND_ASSIGN(HitTestDataProviderMus);
+};
+
+}  // namespace aura
+
+#endif  // UI_AURA_MUS_HIT_TEST_DATA_PROVIDER_MUS_H_