WIP Hittest Component.

components/viz/hit_test/hit_test_aggregator_unittest.cc

Index: components/viz/hit_test/hit_test_aggregator_unittest.cc
diff --git a/components/viz/hit_test/hit_test_aggregator_unittest.cc b/components/viz/hit_test/hit_test_aggregator_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c35120eded373e8575fd7a98ea1c20ed89a71b6d
--- /dev/null
+++ b/components/viz/hit_test/hit_test_aggregator_unittest.cc
@@ -0,0 +1,514 @@
+// 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 "hit_test_aggregator.h"
+#include "cc/surfaces/frame_sink_id.h"
+#include "cc/surfaces/local_surface_id.h"
+#include "cc/surfaces/surface_id.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace viz {
+namespace hit_test {
+namespace test {
+
+namespace {
+
+constexpr cc::FrameSinkId kDisplayFrameSink(2, 0);
+
+cc::SurfaceId MakeSurfaceId(const cc::FrameSinkId& frame_sink_id,
+                            uint32_t local_id) {
+  return cc::SurfaceId(
+      frame_sink_id,
+      cc::LocalSurfaceId(local_id, base::UnguessableToken::Deserialize(0, 1u)));
+}
+
+}  // namespace
+
+using namespace hit_test::mojom;
+
+class HitTestAggregatorTest : public testing::Test {
+ public:
+  HitTestAggregatorTest() {}
+  ~HitTestAggregatorTest() override {}
+
+  void SetUp() override {}
+
+  void TearDown() override {}
+
+  HitTestAggregator aggregator_;
+
+  int count() {
+    DisplayHitTestRegion* start = aggregator_.GetCurrentRegions();
+    DisplayHitTestRegion* end = start;
+    while (end->child_count_ != kEndOfList) {
+      end++;
+    }
+    return end - start;
+  }
+
+  DisplayHitTestRegion* RegionAtIndex(int i) {
+    return aggregator_.GetCurrentRegions() + i;
+  }
+
+  int GetPendingCount() { return aggregator_.pending_.size(); }
+  int GetActiveCount() { return aggregator_.active_.size(); }
+
+  void Reset() {
+    int size = aggregator_.display_hit_test_data_->size_;
+
+    aggregator_.display_hit_test_data_->regions_[0].child_count_ = kEndOfList;
+    aggregator_.display_hit_test_data_->regions_[size >> 1].child_count_ =
+        kEndOfList;
+
+    aggregator_.pending_.clear();
+    aggregator_.active_.clear();
+  }
+};
+
+// tests brainstorm & todo

[rjkroege, 2017/06/07 21:19:06]

you would remove this before landing

[gklassen, 2017/06/08 20:33:21]

ok.  Agreed. Done.

+// child transforms
+// submit late
+// keep surfaces until destroyed
+// bowtie
+
+// one surface

[rjkroege, 2017/06/07 21:19:06]

Love it! Wonderful!

And... comments need to be sentences.

It would be nice to add the ascii art to the display_hit_test_data .h explaining
how the data structure works and reference it here

[gklassen, 2017/06/08 20:33:21]

Agreed.  Or should this be added to an .md?

[rjkroege, 2017/06/09 15:47:07]

I like it here.

[gklassen, 2017/06/12 16:30:41]

Acknowledged.

+//
+//  +----------+
+//  |          |
+//  |          |
+//  |          |
+//  +----------+
+//
+TEST_F(HitTestAggregatorTest, OneSurface) {
+  EXPECT_TRUE(count() == 0);
+
+  cc::SurfaceId display_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+
+  auto hit_test_data = HitTestData::New();
+  hit_test_data->surface_id_ = display_surface_id;
+  hit_test_data->bounds_.SetRect(0, 0, 1024, 768);

[rjkroege, 2017/06/07 21:19:06]

So: in this case, the example receives no events yes? Because it has no region?

Or am I mis-understanding the representation.

[gklassen, 2017/06/08 20:33:21]

I will update based on our conversation this morning. 

+
+  aggregator_.SubmitHitTestData(std::move(hit_test_data));
+
+  EXPECT_TRUE(count() == 0);
+
+  EXPECT_TRUE(GetPendingCount() == 1);
+  EXPECT_TRUE(GetActiveCount() == 0);
+
+  aggregator_.OnSurfaceWillDraw(display_surface_id);
+
+  EXPECT_TRUE(GetPendingCount() == 1);
+  EXPECT_TRUE(GetActiveCount() == 1);
+
+  aggregator_.Aggregate(display_surface_id);
+  aggregator_.Swap();
+
+  // no sub-routing means an empty tree - all events to root

[rjkroege, 2017/06/07 21:19:06]

Ah. I am not misunderstanding.  I hope.

Then you need a case with the same picture but with a region equivalent to the
bounds.

[gklassen, 2017/06/08 20:33:21]

I will update based on our conversation this morning. 

+  EXPECT_TRUE(count() == 0);
+}
+
+// one embedder two regions
+//
+//  +e------------+
+//  | +r1-+ +r2-+ |
+//  | |   | |   | |
+//  | |   | |   | |
+//  | +---+ +---+ |
+//  +-------------+
+//
+TEST_F(HitTestAggregatorTest, OneEmbedderTwoRegions) {
+  Reset();
+  EXPECT_TRUE(count() == 0);
+
+  cc::SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+
+  auto e_hit_test_data = HitTestData::New();
+  e_hit_test_data->surface_id_ = e_surface_id;
+  e_hit_test_data->bounds_.SetRect(0, 0, 1024, 768);
+
+  auto r1_hit_test_region = HitTestRegion::New();
+  r1_hit_test_region->flags_ = HitTestRegionFlags::HIT_TEST_MINE;
+  r1_hit_test_region->rect_.SetRect(0, 0, 512, 512);
+
+  auto r2_hit_test_region = HitTestRegion::New();
+  r2_hit_test_region->flags_ = HitTestRegionFlags::HIT_TEST_MINE;
+  r2_hit_test_region->rect_.SetRect(0, 0, 512, 512);

[rjkroege, 2017/06/07 21:19:06]

the coordinates don't match your picture?

[gklassen, 2017/06/08 20:33:21]

Done.

+
+  e_hit_test_data->regions_.push_back(std::move(r1_hit_test_region));
+  e_hit_test_data->regions_.push_back(std::move(r2_hit_test_region));
+
+  // submit
+
+  EXPECT_TRUE(GetPendingCount() == 0);
+
+  aggregator_.SubmitHitTestData(std::move(e_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 1);
+
+  // surfaces added to DisplayFrame ( in unexpected order )
+
+  EXPECT_TRUE(count() == 0);
+  EXPECT_TRUE(GetActiveCount() == 0);
+
+  aggregator_.OnSurfaceWillDraw(e_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 1);
+
+  // aggregate and swap
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_TRUE(count() == 0);
+
+  aggregator_.Swap();
+  EXPECT_TRUE(count() == 3);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_BOUNDS);
+  EXPECT_TRUE(region->frame_sink_id_ == e_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 1024, 768));
+  EXPECT_TRUE(region->child_count_ == 2);
+
+  region = RegionAtIndex(1);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_MINE);
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 512, 512));
+  EXPECT_TRUE(region->child_count_ == 0);
+
+  region = RegionAtIndex(2);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_MINE);
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 512, 512));
+  EXPECT_TRUE(region->child_count_ == 0);
+}
+
+// one embedder two children
+//
+//  +e------------+
+//  | +c1-+ +c2-+ |
+//  | |   | |   | |
+//  | |   | |   | |
+//  | +---+ +---+ |
+//  +-------------+
+//
+
+TEST_F(HitTestAggregatorTest, OneEmbedderTwoChildren) {
+  Reset();
+  EXPECT_TRUE(count() == 0);
+
+  cc::SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  cc::SurfaceId c1_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+  cc::SurfaceId c2_surface_id = MakeSurfaceId(kDisplayFrameSink, 3);
+
+  auto e_hit_test_data = HitTestData::New();
+  e_hit_test_data->surface_id_ = e_surface_id;
+  e_hit_test_data->bounds_.SetRect(0, 0, 1024, 768);
+
+  auto c1_hit_test_region = HitTestRegion::New();

[rjkroege, 2017/06/07 21:19:06]

this needs a better naming convention: it's the hit test region where c1 goes
but in the parent? as opposed to c1's region

[gklassen, 2017/06/08 20:33:21]

Done.

+  c1_hit_test_region->flags_ = HitTestRegionFlags::HIT_TEST_CHILD_SURFACE;
+  c1_hit_test_region->surface_id_ = c1_surface_id;
+  c1_hit_test_region->rect_.SetRect(0, 0, 512, 512);
+
+  auto c2_hit_test_region = HitTestRegion::New();
+  c2_hit_test_region->flags_ = HitTestRegionFlags::HIT_TEST_CHILD_SURFACE;
+  c2_hit_test_region->surface_id_ = c2_surface_id;
+  c2_hit_test_region->rect_.SetRect(0, 0, 512, 512);

[rjkroege, 2017/06/07 21:19:06]

don't match picture. :-)

[gklassen, 2017/06/08 20:33:21]

Done.

+
+  e_hit_test_data->regions_.push_back(std::move(c1_hit_test_region));
+  e_hit_test_data->regions_.push_back(std::move(c2_hit_test_region));
+
+  auto c1_hit_test_data = HitTestData::New();

[rjkroege, 2017/06/07 21:19:06]

the children don't have bounds?  i.e.: it's a bare HitTestData?

[gklassen, 2017/06/08 20:33:22]

Will update based on conversation this morning. 

+  c1_hit_test_data->surface_id_ = c1_surface_id;
+
+  auto c2_hit_test_data = HitTestData::New();
+  c2_hit_test_data->surface_id_ = c2_surface_id;
+
+  // submit ( in unexpected order )
+
+  EXPECT_TRUE(GetPendingCount() == 0);
+
+  aggregator_.SubmitHitTestData(std::move(c1_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 1);
+
+  aggregator_.SubmitHitTestData(std::move(e_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 2);
+
+  aggregator_.SubmitHitTestData(std::move(c2_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 3);
+
+  // surfaces added to DisplayFrame ( in unexpected order )
+
+  EXPECT_TRUE(count() == 0);
+
+  EXPECT_TRUE(GetActiveCount() == 0);
+
+  aggregator_.OnSurfaceWillDraw(c2_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 1);
+
+  aggregator_.OnSurfaceWillDraw(c1_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 2);
+
+  aggregator_.OnSurfaceWillDraw(e_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 3);
+
+  // aggregate and swap
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_TRUE(count() == 0);
+
+  aggregator_.Swap();
+
+  // we expect 5 entries in the tree - one for one for each child

[rjkroege, 2017/06/07 21:19:06]

Why? The children have no bounds region? or "HIT_TEST_MINE" region?

[gklassen, 2017/06/08 20:33:21]

Will update based on conversation this morning. 

+  EXPECT_TRUE(count() == 3);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_BOUNDS);
+  EXPECT_TRUE(region->frame_sink_id_ == e_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 1024, 768));
+  EXPECT_TRUE(region->child_count_ == 2);
+
+  region = RegionAtIndex(1);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_CHILD_SURFACE);
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 512, 512));
+  EXPECT_TRUE(region->child_count_ == 0);
+
+  region = RegionAtIndex(2);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_CHILD_SURFACE);
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 512, 512));
+  EXPECT_TRUE(region->child_count_ == 0);
+}
+
+// three children deep
+//
+//  +e------------+
+//  | +c1-------+ |
+//  | | +c2---+ | |
+//  | | | +c3-| | |
+//  | | | |   | | |
+//  | | | +---| | |
+//  | | +-----+ | |
+//  | +---------+ |
+//  +-------------+
+//
+
+TEST_F(HitTestAggregatorTest, ThreeChildrenDeep) {
+  Reset();
+  EXPECT_TRUE(count() == 0);
+
+  cc::SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  cc::SurfaceId c1_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+  cc::SurfaceId c2_surface_id = MakeSurfaceId(kDisplayFrameSink, 3);
+  cc::SurfaceId c3_surface_id = MakeSurfaceId(kDisplayFrameSink, 4);
+
+  auto e_hit_test_data = HitTestData::New();
+  e_hit_test_data->surface_id_ = e_surface_id;
+  e_hit_test_data->bounds_.SetRect(0, 0, 800, 800);
+
+  auto c1_hit_test_region = HitTestRegion::New();
+  c1_hit_test_region->flags_ = HitTestRegionFlags::HIT_TEST_CHILD_SURFACE;
+  c1_hit_test_region->surface_id_ = c1_surface_id;
+  c1_hit_test_region->rect_.SetRect(100, 100, 700, 700);
+
+  e_hit_test_data->regions_.push_back(std::move(c1_hit_test_region));
+
+  auto c1_hit_test_data = HitTestData::New();
+  c1_hit_test_data->surface_id_ = c1_surface_id;
+  c1_hit_test_data->bounds_.SetRect(0, 0, 600, 600);
+
+  auto c2_hit_test_region = HitTestRegion::New();
+  c2_hit_test_region->flags_ = HitTestRegionFlags::HIT_TEST_CHILD_SURFACE;
+  c2_hit_test_region->surface_id_ = c2_surface_id;
+  c2_hit_test_region->rect_.SetRect(100, 100, 500, 500);
+
+  c1_hit_test_data->regions_.push_back(std::move(c2_hit_test_region));
+
+  auto c2_hit_test_data = HitTestData::New();
+  c2_hit_test_data->surface_id_ = c2_surface_id;
+  c2_hit_test_data->bounds_.SetRect(0, 0, 400, 400);
+
+  auto c3_hit_test_region = HitTestRegion::New();
+  c3_hit_test_region->flags_ = HitTestRegionFlags::HIT_TEST_CHILD_SURFACE;
+  c3_hit_test_region->surface_id_ = c3_surface_id;
+  c3_hit_test_region->rect_.SetRect(100, 100, 300, 300);
+
+  c2_hit_test_data->regions_.push_back(std::move(c3_hit_test_region));
+
+  auto c3_hit_test_data = HitTestData::New();
+  c3_hit_test_data->surface_id_ = c3_surface_id;
+  c3_hit_test_data->bounds_.SetRect(0, 0, 200, 200);
+
+  // submit ( in unexpected order )
+
+  EXPECT_TRUE(GetPendingCount() == 0);
+
+  aggregator_.SubmitHitTestData(std::move(c1_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 1);
+
+  aggregator_.SubmitHitTestData(std::move(c3_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 2);
+
+  aggregator_.SubmitHitTestData(std::move(e_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 3);
+
+  aggregator_.SubmitHitTestData(std::move(c2_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 4);
+
+  // surfaces added to DisplayFrame ( in unexpected order )
+
+  EXPECT_TRUE(count() == 0);
+
+  EXPECT_TRUE(GetActiveCount() == 0);
+
+  aggregator_.OnSurfaceWillDraw(c2_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 1);
+
+  aggregator_.OnSurfaceWillDraw(c1_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 2);
+
+  aggregator_.OnSurfaceWillDraw(e_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 3);
+
+  aggregator_.OnSurfaceWillDraw(c3_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 4);
+
+  // aggregate and swap
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_TRUE(count() == 0);
+
+  aggregator_.Swap();
+
+  // we expect 3 entries in the tree - one for each child
+  EXPECT_TRUE(count() == 6);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_BOUNDS);
+  EXPECT_TRUE(region->frame_sink_id_ == e_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 800, 800));
+  EXPECT_TRUE(region->child_count_ == 5);
+
+  region = RegionAtIndex(1);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_CHILD_SURFACE);
+  EXPECT_TRUE(region->frame_sink_id_ == c1_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->rect_ == gfx::Rect(100, 100, 700, 700));
+  EXPECT_TRUE(region->child_count_ == 4);
+
+  region = RegionAtIndex(2);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_BOUNDS);
+  EXPECT_TRUE(region->frame_sink_id_ == c1_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 600, 600));
+  EXPECT_TRUE(region->child_count_ == 3);
+
+  region = RegionAtIndex(3);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_CHILD_SURFACE);
+  EXPECT_TRUE(region->frame_sink_id_ == c2_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->rect_ == gfx::Rect(100, 100, 500, 500));
+  EXPECT_TRUE(region->child_count_ == 2);
+
+  region = RegionAtIndex(4);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_BOUNDS);
+  EXPECT_TRUE(region->frame_sink_id_ == c2_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 400, 400));
+  EXPECT_TRUE(region->child_count_ == 1);
+
+  region = RegionAtIndex(5);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_CHILD_SURFACE);
+  EXPECT_TRUE(region->frame_sink_id_ == c3_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->rect_ == gfx::Rect(100, 100, 300, 300));
+  EXPECT_TRUE(region->child_count_ == 0);
+}
+
+// occluded child frame ( OOPIF )
+//
+//  +e-----------+
+//  | +c--+      |
+//  | | +div-+   |
+//  | | |    |   |
+//  | | +----+   |
+//  | +---+      |
+//  +------------+
+//
+
+TEST_F(HitTestAggregatorTest, OccludedChildFrame) {
+  Reset();
+  EXPECT_TRUE(count() == 0);
+
+  cc::SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  cc::SurfaceId c_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+
+  auto e_hit_test_data = HitTestData::New();
+  e_hit_test_data->surface_id_ = e_surface_id;
+  e_hit_test_data->bounds_.SetRect(0, 0, 500, 500);
+
+  auto div_hit_test_region = HitTestRegion::New();
+  div_hit_test_region->flags_ = HitTestRegionFlags::HIT_TEST_MINE;
+  div_hit_test_region->rect_.SetRect(100, 100, 400, 400);
+
+  auto c_hit_test_region = HitTestRegion::New();
+  c_hit_test_region->flags_ = HitTestRegionFlags::HIT_TEST_CHILD_SURFACE;
+  c_hit_test_region->surface_id_ = c_surface_id;
+  c_hit_test_region->rect_.SetRect(200, 200, 500, 200);
+
+  e_hit_test_data->regions_.push_back(std::move(div_hit_test_region));
+  e_hit_test_data->regions_.push_back(std::move(c_hit_test_region));
+
+  auto c_hit_test_data = HitTestData::New();
+  c_hit_test_data->surface_id_ = c_surface_id;
+  c_hit_test_data->bounds_.SetRect(0, 0, 300, 300);
+
+  // submit ( in unexpected order )
+
+  EXPECT_TRUE(GetPendingCount() == 0);
+
+  aggregator_.SubmitHitTestData(std::move(c_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 1);
+
+  aggregator_.SubmitHitTestData(std::move(e_hit_test_data));
+  EXPECT_TRUE(GetPendingCount() == 2);
+
+  // surfaces added to DisplayFrame ( in unexpected order )
+
+  EXPECT_TRUE(count() == 0);
+
+  EXPECT_TRUE(GetActiveCount() == 0);
+
+  aggregator_.OnSurfaceWillDraw(e_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 1);
+
+  aggregator_.OnSurfaceWillDraw(c_surface_id);
+  EXPECT_TRUE(GetActiveCount() == 2);
+
+  // aggregate and swap
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_TRUE(count() == 0);
+
+  aggregator_.Swap();
+
+  EXPECT_TRUE(count() == 3);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_BOUNDS);
+  EXPECT_TRUE(region->frame_sink_id_ == e_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->rect_ == gfx::Rect(0, 0, 500, 500));
+  EXPECT_TRUE(region->child_count_ == 2);
+
+  region = RegionAtIndex(1);

[rjkroege, 2017/06/07 21:19:06]

I would expect an additional region typically yes? The region for the parent
itself?

[gklassen, 2017/06/08 20:33:22]

Will update based on conversation this morning. 

[rjkroege, 2017/06/09 15:47:07]

could type "done" using the handy button to mean that I should see it adjusted
in the next CL

[gklassen, 2017/06/12 16:30:41]

Done.

+  EXPECT_TRUE(region->rect_ == gfx::Rect(100, 100, 400, 400));
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_MINE);
+  EXPECT_TRUE(region->child_count_ == 0);
+
+  region = RegionAtIndex(2);
+  EXPECT_TRUE(region->rect_ == gfx::Rect(200, 200, 500, 200));
+  EXPECT_TRUE(region->frame_sink_id_ == c_surface_id.frame_sink_id());
+  EXPECT_TRUE(region->flags_ == HitTestRegionFlags::HIT_TEST_CHILD_SURFACE);
+  EXPECT_TRUE(region->child_count_ == 0);
+}
+
+}  // namespace test
+}  // namespace hit_test
+}  // namespace viz