Implement HitTestAggregator

components/viz/common/aggregated_hit_test_region.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 COMPONENTS_VIZ_COMMON_AGGREGATED_HIT_TEST_REGION_H_
+#define COMPONENTS_VIZ_COMMON_AGGREGATED_HIT_TEST_REGION_H_
+
+#include <stdint.h>
+
+#include "components/viz/common/surface_id.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/transform.h"
+
+namespace viz {
+
+// A AggregatedHitTestRegion element with child_count of kEndOfList indicates
+// the last element and end of the list.
+constexpr int kEndOfList = -1;
+
+// An array of AggregatedHitTestRegion elements is used to define the
+// aggregated hit-test data for the Display.
+//
+// It is designed to be in shared memory so that the viz service can
+// write the hit_test data, and the viz host can read without
+// process hops.
+

[danakj, 2017/07/13 15:39:38]

nit: remove whitespace between comment and the thing its commenting

[gklassen, 2017/07/13 19:59:13]

Done.

+struct AggregatedHitTestRegion {
+  // The FrameSinkId corresponding to this region.  Events that match
+  // are routed to this surface.
+  FrameSinkId frame_sink_id;
+
+  // Flags to indicate the type of region as defined in
+  // services/viz/public/interfaces/hit_test_region_list.mojom.h.

[danakj, 2017/07/13 15:39:38]

i would specify the namespace+typename rather than the file path.

[gklassen, 2017/07/13 19:59:14]

Done.

+  uint32_t flags;
+
+  // The rectangle that defines the region in parent region's coordinate space.
+  gfx::Rect rect;
+
+  // The transform applied to the rect in parent region's coordinate space.
+  gfx::Transform transform;
+
+  // The number of children including their children below this entry.
+  // If this element is not matched then child_count elements can be skipped
+  // to move to the next entry.
+  int child_count;
+};
+
+}  // namespace viz
+
+#endif  // COMPONENTS_VIZ_COMMON_AGGREGATED_HIT_TEST_REGION_H_