Add viz-host HitTestQuery.

components/viz/host/hit_test/hit_test_query.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_HOST_HIT_TEST_HIT_TEST_QUERY_H_
+#define COMPONENTS_VIZ_HOST_HIT_TEST_HIT_TEST_QUERY_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "components/viz/common/hit_test/display_hit_test_data.h"
+#include "components/viz/common/hit_test/hit_test_export.h"
+#include "ui/gfx/geometry/point.h"
+
+namespace viz {
+namespace hit_test {
+
+struct Target {
+  cc::FrameSinkId id;
+  gfx::Point location_in_target;

[rjkroege, 2017/06/15 19:58:36]

the coordinate system of the target FrameSinkId...

[riajiang, 2017/06/16 02:56:54]

Done.

+  // TODO(riajiang): use HitTestRegionFlags instead of int after
+  // https://codereview.chromium.org/2908783002/
+  int flags;

[gklassen, 2017/06/15 19:51:20]

flags are now a uint32 instead of HitTesRegionFlags in 2908783002 as well ( it
seemed to be necessary to enable or'ing of multiple flags ) - so this can likely
stay but you may want to use a uint32 to match. 

[riajiang, 2017/06/16 02:56:54]

Ah I see, changed to uint32.

+};
+
+// Finds the target for a given location based on DisplayHitTestData aggreated
+// by HitTestComponent.
+class HIT_TEST_EXPORT HitTestQuery {
+ public:
+  HitTestQuery();
+  ~HitTestQuery();
+
+  // TODO(riajiang): Read from shmem directly once it's set up and delete this
+  // function. For now, use fake data.
+  void set_display_hit_test_data_list(
+      std::vector<DisplayHitTestData> display_hit_test_data_list) {
+    display_hit_test_data_list_ = display_hit_test_data_list;
+  }
+
+  // Find Target for |location_in_root|, including the FrameSinkId of the
+  // target, updated location in the coordinate system of the target and
+  // hit-test flags for the target.
+  Target FindTargetForLocation(const gfx::Point& location_in_root);

[rjkroege, 2017/06/15 19:58:36]

You have written the code that does the event dispatching right?

Where will the code that asks blink for help? Is this part of the public API?
You need to explain this to me

[riajiang, 2017/06/16 02:56:54]

https://cs.chromium.org/chromium/src/services/ui/ws/event_targeter.cc?type=cs...
is where I think we can put all these. It would first try to get the FrameSinkId
from HitTestQuery and if not successful, do an async call to ask Blink for help.

+
+ private:
+  std::vector<DisplayHitTestData> display_hit_test_data_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(HitTestQuery);
+};
+
+}  // namespace hit_test
+}  // namespace viz
+
+#endif  // COMPONENTS_VIZ_HOST_HIT_TEST_HIT_TEST_QUERY_H_