Implement HitTestAggregator

components/viz/common/display_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_DISPLAY_HIT_TEST_REGION_H_
+#define COMPONENTS_VIZ_COMMON_DISPLAY_HIT_TEST_REGION_H_
+
+#include <stdint.h>
+
+#include "cc/surfaces/surface_id.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/transform.h"
+
+namespace viz {
+
+// An array of DisplayHitTestRegion elements is used to define the

[danakj, 2017/06/30 20:39:38]

put this comment directly above the struct definition, so it is anchored to it.

[gklassen, 2017/07/12 14:43:51]

Done.

+// aggregated hit-test data for the Display.
+//
+// It is designed to be in shared memory so that the viz process can

[danakj, 2017/06/30 20:39:38]

viz service can write

[gklassen, 2017/07/12 14:43:51]

Done.

+// write the hit_test data, and the browser / ws process can read without

[danakj, 2017/06/30 20:39:38]

the viz host can read

[gklassen, 2017/07/12 14:43:51]

Done.

+// process hops.
+
+// A DisplayHitTestRegion element with child_count of kEndOfList indicates
+// the last element and end of the list.
+constexpr int kEndOfList = -1;
+
+struct DisplayHitTestRegion {

[danakj, 2017/06/30 20:39:38]

I suggest AggregatedHitTestRegion, because HitTestRegion is also somehow related
to Displays, so I found it hard to understand what is the difference.

[gklassen, 2017/07/12 14:43:51]

Done.

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