Add viz-host HitTestQuery.

components/viz/host/hit_test/hit_test_query.cc

+// 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.
+
+#include "components/viz/host/hit_test/hit_test_query.h"
+
+#include "services/viz/hit_test/public/interfaces/hit_test_region_list.mojom.h"
+
+namespace viz {
+
+HitTestQuery::HitTestQuery() = default;
+
+HitTestQuery::~HitTestQuery() = default;
+
+Target HitTestQuery::FindTargetForLocation(
+    const gfx::Point& location_in_root) const {
+  Target target;
+  if (!aggregated_hit_test_region_list_size_)
+    return target;
+
+  FindTargetInRegionForLocation(location_in_root,
+                                aggregated_hit_test_region_list_, &target);
+  return target;
+}
+
+bool HitTestQuery::FindTargetInRegionForLocation(
+    const gfx::Point& location_in_parent,
+    AggregatedHitTestRegion* region,
+    Target* target) const {
+  gfx::Point location_transformed(location_in_parent);
+  region->transform.TransformPoint(&location_transformed);
+  if (!region->rect.Contains(location_transformed))
+    return false;
+
+  if (region->child_count < 0 ||
+      region->child_count >
+          (aggregated_hit_test_region_list_ +
+           aggregated_hit_test_region_list_size_ - region - 1)) {
+    return false;
+  }
+  AggregatedHitTestRegion* child_region = region + 1;
+  AggregatedHitTestRegion* child_region_end =
+      child_region + region->child_count;
+  gfx::Point location_in_target(location_transformed);
+  location_in_target.Offset(-region->rect.x(), -region->rect.y());
+  while (child_region < child_region_end) {
+    if (FindTargetInRegionForLocation(location_in_target, child_region,
+                                      target)) {
+      return true;
+    }
+
+    if (child_region->child_count < 0 ||
+        child_region->child_count >= region->child_count) {
+      return false;
+    }
+    child_region = child_region + child_region->child_count + 1;
+  }
+
+  if (region->flags & mojom::kHitTestMine) {
+    target->frame_sink_id = region->frame_sink_id;
+    target->location_in_target = location_in_target;
+    target->flags = region->flags;
+    return true;
+  }
+  return false;
+}
+
+}  // namespace viz