Implement HitTestAggregator

components/viz/service/hit_test/hit_test_aggregator_unittest.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/service/hit_test/hit_test_aggregator.h"
+
+#include "components/viz/common/surfaces/frame_sink_id.h"
+#include "components/viz/common/surfaces/local_surface_id.h"
+#include "components/viz/common/surfaces/surface_id.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace viz {
+
+namespace {
+
+constexpr FrameSinkId kDisplayFrameSink(2, 0);
+
+SurfaceId MakeSurfaceId(const FrameSinkId& frame_sink_id, uint32_t local_id) {
+  return SurfaceId(
+      frame_sink_id,
+      LocalSurfaceId(local_id, base::UnguessableToken::Deserialize(0, 1u)));
+}
+
+}  // namespace
+
+class TestHitTestAggregator : public HitTestAggregator {
+ public:
+  TestHitTestAggregator() = default;
+  ~TestHitTestAggregator() = default;
+
+  void CallOnSurfaceWillDraw(SurfaceId surface_id) {
+    OnSurfaceWillDraw(surface_id);
+  }
+  void CallOnSurfaceDiscarded(SurfaceId surface_id) {
+    OnSurfaceDiscarded(surface_id);
+  }
+
+  int Count() {
+    AggregatedHitTestRegion* start =
+        static_cast<AggregatedHitTestRegion*>(read_buffer_.get());
+    AggregatedHitTestRegion* end = start;
+    while (end->child_count != kEndOfList)
+      end++;
+
+    int count = end - start;
+    return count;
+  }
+  int GetPendingCount() { return pending_.size(); }
+  int GetActiveCount() { return active_.size(); }
+  int GetActiveRegionCount() { return active_region_count_; }
+  int GetHitTestRegionListSize() { return read_size_; }
+  AggregatedHitTestRegion* GetRegions() {
+    return static_cast<AggregatedHitTestRegion*>(read_buffer_.get());
+  }
+
+  void Reset() {
+    AggregatedHitTestRegion* regions =
+        static_cast<AggregatedHitTestRegion*>(write_buffer_.get());
+    regions[0].child_count = kEndOfList;
+
+    regions = static_cast<AggregatedHitTestRegion*>(read_buffer_.get());
+    regions[0].child_count = kEndOfList;
+
+    pending_.clear();
+    active_.clear();
+  }
+};
+
+class HitTestAggregatorTest : public testing::Test {
+ public:
+  HitTestAggregatorTest() = default;
+  ~HitTestAggregatorTest() override = default;
+
+  // testing::Test:
+  void SetUp() override {}
+  void TearDown() override { aggregator_.Reset(); }
+
+  TestHitTestAggregator aggregator_;
+
+  // Creates a hit test data element with 8 children recursively to
+  // the specified depth.  SurfaceIds are generated in sequential order and
+  // the method returns the next unused id.
+  int CreateAndSubmitHitTestRegionListWith8Children(int id, int depth) {
+    SurfaceId surface_id = MakeSurfaceId(kDisplayFrameSink, id);
+    id++;
+
+    auto hit_test_region_list = mojom::HitTestRegionList::New();
+    hit_test_region_list->surface_id = surface_id;
+    hit_test_region_list->flags = mojom::kHitTestMine;
+    hit_test_region_list->bounds.SetRect(0, 0, 1024, 768);
+
+    for (int i = 0; i < 8; i++) {
+      auto hit_test_region = mojom::HitTestRegion::New();
+      hit_test_region->rect.SetRect(100, 100, 100, 100);
+
+      if (depth > 0) {
+        hit_test_region->flags = mojom::kHitTestChildSurface;
+        hit_test_region->surface_id = MakeSurfaceId(kDisplayFrameSink, id);
+        id = CreateAndSubmitHitTestRegionListWith8Children(id, depth - 1);
+      } else {
+        hit_test_region->flags = mojom::kHitTestMine;
+      }
+      hit_test_region_list->regions.push_back(std::move(hit_test_region));
+    }
+
+    aggregator_.SubmitHitTestRegionList(std::move(hit_test_region_list));
+    return id;
+  }
+};
+
+// TODO(gklassen): Add tests for 3D use cases as suggested by and with
+// input from rjkroege.
+
+// One surface.
+//
+//  +----------+
+//  |          |
+//  |          |
+//  |          |
+//  +----------+
+//
+TEST_F(HitTestAggregatorTest, OneSurface) {
+  EXPECT_EQ(0, aggregator_.Count());
+
+  SurfaceId display_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+
+  auto hit_test_region_list = mojom::HitTestRegionList::New();
+  hit_test_region_list->surface_id = display_surface_id;
+  hit_test_region_list->flags = mojom::kHitTestMine;
+  hit_test_region_list->bounds.SetRect(0, 0, 1024, 768);
+
+  aggregator_.SubmitHitTestRegionList(std::move(hit_test_region_list));
+  EXPECT_EQ(0, aggregator_.Count());
+
+  EXPECT_EQ(1, aggregator_.GetPendingCount());
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(display_surface_id);
+
+  EXPECT_EQ(0, aggregator_.GetPendingCount());
+  EXPECT_EQ(1, aggregator_.GetActiveCount());
+
+  aggregator_.Aggregate(display_surface_id);
+  aggregator_.Swap();
+
+  // Expect 1 entry routing all events to the one surface (display root).
+  EXPECT_EQ(1, aggregator_.Count());
+
+  AggregatedHitTestRegion* regions = aggregator_.GetRegions();
+
+  AggregatedHitTestRegion* region = nullptr;
+
+  region = &regions[0];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(display_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 0, 1024, 768), region->rect);
+  EXPECT_EQ(0, region->child_count);
+}
+
+// One opaque embedder with two regions.
+//
+//  +e-------------+
+//  | +r1-+ +r2--+ |
+//  | |   | |    | |
+//  | |   | |    | |
+//  | +---+ +----+ |
+//  +--------------+
+//
+TEST_F(HitTestAggregatorTest, OneEmbedderTwoRegions) {
+  EXPECT_EQ(0, aggregator_.Count());
+
+  SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+
+  auto e_hit_test_data = mojom::HitTestRegionList::New();
+  e_hit_test_data->surface_id = e_surface_id;
+  e_hit_test_data->flags = mojom::kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_r1 = mojom::HitTestRegion::New();
+  e_hit_test_region_r1->flags = mojom::kHitTestMine;
+  e_hit_test_region_r1->rect.SetRect(100, 100, 200, 400);
+
+  auto e_hit_test_region_r2 = mojom::HitTestRegion::New();
+  e_hit_test_region_r2->flags = mojom::kHitTestMine;
+  e_hit_test_region_r2->rect.SetRect(400, 100, 300, 400);
+
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_r1));
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_r2));
+
+  // Submit mojom::HitTestRegionList.
+
+  EXPECT_EQ(0, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(e_hit_test_data));
+  EXPECT_EQ(1, aggregator_.GetPendingCount());
+
+  // Add Surfaces to DisplayFrame in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.Count());
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(1, aggregator_.GetActiveCount());
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(0, aggregator_.Count());
+
+  aggregator_.Swap();
+  EXPECT_EQ(3, aggregator_.Count());
+
+  AggregatedHitTestRegion* regions = aggregator_.GetRegions();
+
+  AggregatedHitTestRegion* region = nullptr;
+
+  region = &regions[0];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 0, 1024, 768), region->rect);
+  EXPECT_EQ(2, region->child_count);
+
+  region = &regions[1];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(gfx::Rect(100, 100, 200, 400), region->rect);
+  EXPECT_EQ(0, region->child_count);
+
+  region = &regions[2];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(gfx::Rect(400, 100, 300, 400), region->rect);
+  EXPECT_EQ(0, region->child_count);
+}
+
+// One embedder with two children.
+//
+//  +e-------------+
+//  | +c1-+ +c2--+ |
+//  | |   | |    | |
+//  | |   | |    | |
+//  | +---+ +----+ |
+//  +--------------+
+//
+
+TEST_F(HitTestAggregatorTest, OneEmbedderTwoChildren) {
+  EXPECT_EQ(0, aggregator_.Count());
+
+  SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  SurfaceId c1_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+  SurfaceId c2_surface_id = MakeSurfaceId(kDisplayFrameSink, 3);
+
+  auto e_hit_test_data = mojom::HitTestRegionList::New();
+  e_hit_test_data->surface_id = e_surface_id;
+  e_hit_test_data->flags = mojom::kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_c1 = mojom::HitTestRegion::New();
+  e_hit_test_region_c1->flags = mojom::kHitTestChildSurface;
+  e_hit_test_region_c1->surface_id = c1_surface_id;
+  e_hit_test_region_c1->rect.SetRect(100, 100, 200, 300);
+
+  auto e_hit_test_region_c2 = mojom::HitTestRegion::New();
+  e_hit_test_region_c2->flags = mojom::kHitTestChildSurface;
+  e_hit_test_region_c2->surface_id = c2_surface_id;
+  e_hit_test_region_c2->rect.SetRect(400, 100, 400, 300);
+
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_c1));
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_c2));
+
+  auto c1_hit_test_data = mojom::HitTestRegionList::New();
+  c1_hit_test_data->surface_id = c1_surface_id;
+
+  auto c2_hit_test_data = mojom::HitTestRegionList::New();
+  c2_hit_test_data->surface_id = c2_surface_id;
+
+  // Submit in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(c1_hit_test_data));
+  EXPECT_EQ(1, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(e_hit_test_data));
+  EXPECT_EQ(2, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(c2_hit_test_data));
+  EXPECT_EQ(3, aggregator_.GetPendingCount());
+
+  // Surfaces added to DisplayFrame in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.Count());
+
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(c2_surface_id);
+  EXPECT_EQ(1, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(c1_surface_id);
+  EXPECT_EQ(2, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(3, aggregator_.GetActiveCount());
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(0, aggregator_.Count());
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(3, aggregator_.Count());
+
+  AggregatedHitTestRegion* regions = aggregator_.GetRegions();
+
+  AggregatedHitTestRegion* region = nullptr;
+
+  region = &regions[0];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 0, 1024, 768), region->rect);
+  EXPECT_EQ(2, region->child_count);
+
+  region = &regions[1];
+  EXPECT_EQ(mojom::kHitTestChildSurface, region->flags);
+  EXPECT_EQ(c1_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(100, 100, 200, 300), region->rect);
+  EXPECT_EQ(0, region->child_count);
+
+  region = &regions[2];
+  EXPECT_EQ(mojom::kHitTestChildSurface, region->flags);
+  EXPECT_EQ(c2_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(400, 100, 400, 300), region->rect);
+  EXPECT_EQ(0, region->child_count);
+}
+
+// Occluded child frame (OOPIF).
+//
+//  +e-----------+
+//  | +c--+      |
+//  | | +div-+   |
+//  | | |    |   |
+//  | | +----+   |
+//  | +---+      |
+//  +------------+
+//
+
+TEST_F(HitTestAggregatorTest, OccludedChildFrame) {
+  EXPECT_EQ(0, aggregator_.Count());
+
+  SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  SurfaceId c_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+
+  auto e_hit_test_data = mojom::HitTestRegionList::New();
+  e_hit_test_data->surface_id = e_surface_id;
+  e_hit_test_data->flags = mojom::kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_div = mojom::HitTestRegion::New();
+  e_hit_test_region_div->flags = mojom::kHitTestMine;
+  e_hit_test_region_div->surface_id = e_surface_id;
+  e_hit_test_region_div->rect.SetRect(200, 200, 300, 200);
+
+  auto e_hit_test_region_c = mojom::HitTestRegion::New();
+  e_hit_test_region_c->flags = mojom::kHitTestChildSurface;
+  e_hit_test_region_c->surface_id = c_surface_id;
+  e_hit_test_region_c->rect.SetRect(100, 100, 200, 500);
+
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_div));
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_c));
+
+  auto c_hit_test_data = mojom::HitTestRegionList::New();
+  c_hit_test_data->surface_id = c_surface_id;
+  c_hit_test_data->flags = mojom::kHitTestMine;
+  c_hit_test_data->bounds.SetRect(0, 0, 200, 500);
+
+  // Submit in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(c_hit_test_data));
+  EXPECT_EQ(1, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(e_hit_test_data));
+  EXPECT_EQ(2, aggregator_.GetPendingCount());
+
+  // Surfaces added to DisplayFrame in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.Count());
+
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(1, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(c_surface_id);
+  EXPECT_EQ(2, aggregator_.GetActiveCount());
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(0, aggregator_.Count());
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(3, aggregator_.Count());
+
+  AggregatedHitTestRegion* regions = aggregator_.GetRegions();
+
+  AggregatedHitTestRegion* region = nullptr;
+
+  region = &regions[0];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 0, 1024, 768), region->rect);
+  EXPECT_EQ(2, region->child_count);
+
+  region = &regions[1];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(200, 200, 300, 200), region->rect);
+  EXPECT_EQ(0, region->child_count);
+
+  region = &regions[2];
+  EXPECT_EQ(region->flags, mojom::kHitTestChildSurface | mojom::kHitTestMine);
+  EXPECT_EQ(c_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(100, 100, 200, 500), region->rect);
+  EXPECT_EQ(0, region->child_count);
+}
+
+// Foreground child frame (OOPIF).
+// Same as the previous test except the child is foreground.
+//
+//  +e-----------+
+//  | +c--+      |
+//  | |   |div-+ |
+//  | |   |    | |
+//  | |   |----+ |
+//  | +---+      |
+//  +------------+
+//
+
+TEST_F(HitTestAggregatorTest, ForegroundChildFrame) {
+  EXPECT_EQ(0, aggregator_.Count());
+
+  SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  SurfaceId c_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+
+  auto e_hit_test_data = mojom::HitTestRegionList::New();
+  e_hit_test_data->surface_id = e_surface_id;
+  e_hit_test_data->flags = mojom::kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_div = mojom::HitTestRegion::New();
+  e_hit_test_region_div->flags = mojom::kHitTestMine;
+  e_hit_test_region_div->surface_id = e_surface_id;
+  e_hit_test_region_div->rect.SetRect(200, 200, 300, 200);
+
+  auto e_hit_test_region_c = mojom::HitTestRegion::New();
+  e_hit_test_region_c->flags = mojom::kHitTestChildSurface;
+  e_hit_test_region_c->surface_id = c_surface_id;
+  e_hit_test_region_c->rect.SetRect(100, 100, 200, 500);
+
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_c));
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_div));
+
+  auto c_hit_test_data = mojom::HitTestRegionList::New();
+  c_hit_test_data->surface_id = c_surface_id;
+  c_hit_test_data->flags = mojom::kHitTestMine;
+  c_hit_test_data->bounds.SetRect(0, 0, 200, 500);
+
+  // Submit in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(c_hit_test_data));
+  EXPECT_EQ(1, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(e_hit_test_data));
+  EXPECT_EQ(2, aggregator_.GetPendingCount());
+
+  // Surfaces added to DisplayFrame in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.Count());
+
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(1, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(c_surface_id);
+  EXPECT_EQ(2, aggregator_.GetActiveCount());
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(0, aggregator_.Count());
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(3, aggregator_.Count());
+
+  AggregatedHitTestRegion* regions = aggregator_.GetRegions();
+
+  AggregatedHitTestRegion* region = nullptr;
+
+  region = &regions[0];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 0, 1024, 768), region->rect);
+  EXPECT_EQ(2, region->child_count);
+
+  region = &regions[1];
+  EXPECT_EQ(region->flags, mojom::kHitTestChildSurface | mojom::kHitTestMine);
+  EXPECT_EQ(c_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(100, 100, 200, 500), region->rect);
+  EXPECT_EQ(0, region->child_count);
+
+  region = &regions[2];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(200, 200, 300, 200), region->rect);
+  EXPECT_EQ(0, region->child_count);
+}
+
+// One embedder with a clipped child with a tab and transparent background.
+//
+//  +e-------------+
+//  |   +c---------|     Point   maps to
+//  | 1 |+a--+     |     -----   -------
+//  |   || 2 |  3  |       1        e
+//  |   |+b--------|       2        a
+//  |   ||         |       3        e (transparent area in c)
+//  |   ||   4     |       4        b
+//  +--------------+
+//
+
+TEST_F(HitTestAggregatorTest, ClippedChildWithTabAndTransparentBackground) {
+  EXPECT_EQ(0, aggregator_.Count());
+
+  SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  SurfaceId c_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+  SurfaceId a_surface_id = MakeSurfaceId(kDisplayFrameSink, 3);
+  SurfaceId b_surface_id = MakeSurfaceId(kDisplayFrameSink, 4);
+
+  auto e_hit_test_data = mojom::HitTestRegionList::New();
+  e_hit_test_data->surface_id = e_surface_id;
+  e_hit_test_data->flags = mojom::kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_c = mojom::HitTestRegion::New();
+  e_hit_test_region_c->flags = mojom::kHitTestChildSurface;
+  e_hit_test_region_c->surface_id = c_surface_id;
+  e_hit_test_region_c->rect.SetRect(200, 100, 1600, 800);
+  e_hit_test_region_c->transform.Translate(200, 100);
+
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_c));
+
+  auto c_hit_test_data = mojom::HitTestRegionList::New();
+  c_hit_test_data->surface_id = c_surface_id;
+  c_hit_test_data->flags = mojom::kHitTestIgnore;
+  c_hit_test_data->bounds.SetRect(0, 0, 1600, 800);
+
+  auto c_hit_test_region_a = mojom::HitTestRegion::New();
+  c_hit_test_region_a->flags = mojom::kHitTestChildSurface;
+  c_hit_test_region_a->surface_id = a_surface_id;
+  c_hit_test_region_a->rect.SetRect(0, 0, 200, 100);
+
+  auto c_hit_test_region_b = mojom::HitTestRegion::New();
+  c_hit_test_region_b->flags = mojom::kHitTestChildSurface;
+  c_hit_test_region_b->surface_id = b_surface_id;
+  c_hit_test_region_b->rect.SetRect(0, 100, 800, 600);
+
+  c_hit_test_data->regions.push_back(std::move(c_hit_test_region_a));
+  c_hit_test_data->regions.push_back(std::move(c_hit_test_region_b));
+
+  auto a_hit_test_data = mojom::HitTestRegionList::New();
+  a_hit_test_data->surface_id = a_surface_id;
+  a_hit_test_data->flags = mojom::kHitTestMine;
+  a_hit_test_data->bounds.SetRect(0, 0, 200, 100);
+
+  auto b_hit_test_data = mojom::HitTestRegionList::New();
+  b_hit_test_data->surface_id = b_surface_id;
+  b_hit_test_data->flags = mojom::kHitTestMine;
+  b_hit_test_data->bounds.SetRect(0, 100, 800, 600);
+
+  // Submit in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(c_hit_test_data));
+  EXPECT_EQ(1, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(a_hit_test_data));
+  EXPECT_EQ(2, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(b_hit_test_data));
+  EXPECT_EQ(3, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(e_hit_test_data));
+  EXPECT_EQ(4, aggregator_.GetPendingCount());
+
+  // Surfaces added to DisplayFrame in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.Count());
+
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(c_surface_id);
+  EXPECT_EQ(1, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(2, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(b_surface_id);
+  EXPECT_EQ(3, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(a_surface_id);
+  EXPECT_EQ(4, aggregator_.GetActiveCount());
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(0, aggregator_.Count());
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(4, aggregator_.Count());
+
+  AggregatedHitTestRegion* regions = aggregator_.GetRegions();
+
+  AggregatedHitTestRegion* region = nullptr;
+
+  region = &regions[0];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 0, 1024, 768), region->rect);
+  EXPECT_EQ(3, region->child_count);
+
+  region = &regions[1];
+  EXPECT_EQ(region->flags, mojom::kHitTestChildSurface | mojom::kHitTestIgnore);
+  EXPECT_EQ(c_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(200, 100, 1600, 800), region->rect);
+  EXPECT_EQ(2, region->child_count);
+
+  gfx::Point point(300, 300);
+  region->transform.TransformPointReverse(&point);
+  EXPECT_TRUE(point == gfx::Point(100, 200));
+
+  region = &regions[2];
+  EXPECT_EQ(region->flags, mojom::kHitTestChildSurface | mojom::kHitTestMine);
+  EXPECT_EQ(a_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 0, 200, 100), region->rect);
+  EXPECT_EQ(0, region->child_count);
+
+  region = &regions[3];
+  EXPECT_EQ(region->flags, mojom::kHitTestChildSurface | mojom::kHitTestMine);
+  EXPECT_EQ(b_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 100, 800, 600), region->rect);
+  EXPECT_EQ(0, region->child_count);
+}
+
+// Three children deep.
+//
+//  +e------------+
+//  | +c1-------+ |
+//  | | +c2---+ | |
+//  | | | +c3-| | |
+//  | | | |   | | |
+//  | | | +---| | |
+//  | | +-----+ | |
+//  | +---------+ |
+//  +-------------+
+//
+
+TEST_F(HitTestAggregatorTest, ThreeChildrenDeep) {
+  EXPECT_EQ(0, aggregator_.Count());
+
+  SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  SurfaceId c1_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+  SurfaceId c2_surface_id = MakeSurfaceId(kDisplayFrameSink, 3);
+  SurfaceId c3_surface_id = MakeSurfaceId(kDisplayFrameSink, 4);
+
+  auto e_hit_test_data = mojom::HitTestRegionList::New();
+  e_hit_test_data->surface_id = e_surface_id;
+  e_hit_test_data->flags = mojom::kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_c1 = mojom::HitTestRegion::New();
+  e_hit_test_region_c1->flags = mojom::kHitTestChildSurface;
+  e_hit_test_region_c1->surface_id = c1_surface_id;
+  e_hit_test_region_c1->rect.SetRect(100, 100, 700, 700);
+
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_c1));
+
+  auto c1_hit_test_data = mojom::HitTestRegionList::New();
+  c1_hit_test_data->surface_id = c1_surface_id;
+  c1_hit_test_data->flags = mojom::kHitTestMine;
+  c1_hit_test_data->bounds.SetRect(0, 0, 600, 600);
+
+  auto c1_hit_test_region_c2 = mojom::HitTestRegion::New();
+  c1_hit_test_region_c2->flags = mojom::kHitTestChildSurface;
+  c1_hit_test_region_c2->surface_id = c2_surface_id;
+  c1_hit_test_region_c2->rect.SetRect(100, 100, 500, 500);
+
+  c1_hit_test_data->regions.push_back(std::move(c1_hit_test_region_c2));
+
+  auto c2_hit_test_data = mojom::HitTestRegionList::New();
+  c2_hit_test_data->surface_id = c2_surface_id;
+  c2_hit_test_data->flags = mojom::kHitTestMine;
+  c2_hit_test_data->bounds.SetRect(0, 0, 400, 400);
+
+  auto c2_hit_test_region_c3 = mojom::HitTestRegion::New();
+  c2_hit_test_region_c3->flags = mojom::kHitTestChildSurface;
+  c2_hit_test_region_c3->surface_id = c3_surface_id;
+  c2_hit_test_region_c3->rect.SetRect(100, 100, 300, 300);
+
+  c2_hit_test_data->regions.push_back(std::move(c2_hit_test_region_c3));
+
+  auto c3_hit_test_data = mojom::HitTestRegionList::New();
+  c3_hit_test_data->surface_id = c3_surface_id;
+  c3_hit_test_data->flags = mojom::kHitTestMine;
+  c3_hit_test_data->bounds.SetRect(0, 0, 200, 200);
+
+  // Submit in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(c1_hit_test_data));
+  EXPECT_EQ(1, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(c3_hit_test_data));
+  EXPECT_EQ(2, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(e_hit_test_data));
+  EXPECT_EQ(3, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(c2_hit_test_data));
+  EXPECT_EQ(4, aggregator_.GetPendingCount());
+
+  // Surfaces added to DisplayFrame in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.Count());
+
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(c2_surface_id);
+  EXPECT_EQ(1, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(c1_surface_id);
+  EXPECT_EQ(2, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(3, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(c3_surface_id);
+  EXPECT_EQ(4, aggregator_.GetActiveCount());
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(0, aggregator_.Count());
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(4, aggregator_.Count());
+
+  AggregatedHitTestRegion* regions = aggregator_.GetRegions();
+
+  AggregatedHitTestRegion* region = nullptr;
+
+  region = &regions[0];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 0, 1024, 768), region->rect);
+  EXPECT_EQ(3, region->child_count);
+
+  region = &regions[1];
+  EXPECT_EQ(region->flags, mojom::kHitTestChildSurface | mojom::kHitTestMine);
+  EXPECT_EQ(c1_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(100, 100, 700, 700), region->rect);
+  EXPECT_EQ(2, region->child_count);
+
+  region = &regions[2];
+  EXPECT_EQ(region->flags, mojom::kHitTestChildSurface | mojom::kHitTestMine);
+  EXPECT_EQ(c2_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(100, 100, 500, 500), region->rect);
+  EXPECT_EQ(1, region->child_count);
+
+  region = &regions[3];
+  EXPECT_EQ(region->flags, mojom::kHitTestChildSurface | mojom::kHitTestMine);
+  EXPECT_EQ(c3_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(100, 100, 300, 300), region->rect);
+  EXPECT_EQ(0, region->child_count);
+}
+
+// Missing / late child.
+//
+//  +e-----------+
+//  | +c--+      |
+//  | |   |div-+ |
+//  | |   |    | |
+//  | |   |----+ |
+//  | +---+      |
+//  +------------+
+//
+
+TEST_F(HitTestAggregatorTest, MissingChildFrame) {
+  EXPECT_EQ(0, aggregator_.Count());
+
+  SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  SurfaceId c_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+
+  auto e_hit_test_data = mojom::HitTestRegionList::New();
+  e_hit_test_data->surface_id = e_surface_id;
+  e_hit_test_data->flags = mojom::kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_div = mojom::HitTestRegion::New();
+  e_hit_test_region_div->flags = mojom::kHitTestMine;
+  e_hit_test_region_div->surface_id = e_surface_id;
+  e_hit_test_region_div->rect.SetRect(200, 200, 300, 200);
+
+  auto e_hit_test_region_c = mojom::HitTestRegion::New();
+  e_hit_test_region_c->flags = mojom::kHitTestChildSurface;
+  e_hit_test_region_c->surface_id = c_surface_id;
+  e_hit_test_region_c->rect.SetRect(100, 100, 200, 500);
+
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_c));
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_div));
+
+  auto c_hit_test_data = mojom::HitTestRegionList::New();
+  c_hit_test_data->surface_id = c_surface_id;
+  c_hit_test_data->flags = mojom::kHitTestMine;
+  c_hit_test_data->bounds.SetRect(0, 0, 200, 500);
+
+  // Submit in unexpected order, but not the child.
+
+  EXPECT_EQ(0, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(e_hit_test_data));
+  EXPECT_EQ(1, aggregator_.GetPendingCount());
+
+  // Surfaces added to DisplayFrame in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.Count());
+
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(1, aggregator_.GetActiveCount());
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(0, aggregator_.Count());
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(2, aggregator_.Count());
+
+  AggregatedHitTestRegion* regions = aggregator_.GetRegions();
+
+  AggregatedHitTestRegion* region = nullptr;
+
+  region = &regions[0];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(0, 0, 1024, 768), region->rect);
+  EXPECT_EQ(1, region->child_count);
+
+  // Child would exist here but it was not included in the Display Frame.
+
+  region = &regions[1];
+  EXPECT_EQ(mojom::kHitTestMine, region->flags);
+  EXPECT_EQ(e_surface_id.frame_sink_id(), region->frame_sink_id);
+  EXPECT_EQ(gfx::Rect(200, 200, 300, 200), region->rect);
+  EXPECT_EQ(0, region->child_count);
+}
+
+// Exceed limits to ensure that bounds and resize work.
+//
+// A tree of embedders each with 8 children and 4 levels deep = 4096 regions.
+// This will exceed initial allocation and force a resize.
+//
+//  +e--------------------------------------------------------+
+//  | +c1----------++c2----------++c3----------++c4----------+|
+//  | | +c1--------|| +c1--------|| +c1--------|| +c1--------||
+//  | | | +c1-++c2-|| | +c1-++c2-|| | +c1-++c2-|| | +c1-++c2-||
+//  | | | |   ||   || | |   ||   || | |   ||   || | |   ||   ||
+//  | | | +---++---|| | +---++---|| | +---++---|| | +---++---||
+//  | +------------++------------++------------++------------+|
+//  | +c5----------++c6----------++c7----------++c8----------+|
+//  | | +c1--------|| +c1--------|| +c1--------|| +c1--------||
+//  | | | +c1-++c2-|| | +c1-++c2-|| | +c1-++c2-|| | +c1-++c2-||
+//  | | | |   ||   || | |   ||   || | |   ||   || | |   ||   ||
+//  | | | +---++---|| | +---++---|| | +---++---|| | +---++---||
+//  | +------------++------------++------------++------------+|
+//  +---------------------------------------------------------+
+//
+
+TEST_F(HitTestAggregatorTest, ExceedLimits) {
+  EXPECT_EQ(0, aggregator_.Count());
+
+  EXPECT_LT(aggregator_.GetHitTestRegionListSize(), 4096);
+
+  SurfaceId display_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+
+  int next_surface_id = CreateAndSubmitHitTestRegionListWith8Children(1, 3);
+  int surface_count = next_surface_id - 1;
+
+  EXPECT_EQ(surface_count, aggregator_.GetPendingCount());
+
+  // Mark Surfaces as added to DisplayFrame in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.Count());
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  for (int i = 1; i <= surface_count; i++) {
+    SurfaceId surface_id = MakeSurfaceId(kDisplayFrameSink, i);
+    aggregator_.CallOnSurfaceWillDraw(surface_id);
+  }
+
+  EXPECT_EQ(surface_count, aggregator_.GetActiveCount());
+
+  // Aggregate and swap.
+  aggregator_.Aggregate(display_surface_id);
+  EXPECT_EQ(0, aggregator_.Count());
+
+  aggregator_.Swap();
+
+  // Expect 4680 regions:
+  //  8 children 4 levels deep 8*8*8*8 is  4096
+  //  1 region for each embedder/surface +  584
+  //  1 root                             +    1
+  //                                      -----
+  //                                       4681.
+  EXPECT_EQ(4681, aggregator_.Count());
+
+  EXPECT_GE(aggregator_.GetHitTestRegionListSize(), 4681);
+}
+
+TEST_F(HitTestAggregatorTest, ActiveRegionCount) {
+  EXPECT_EQ(0, aggregator_.GetActiveRegionCount());
+
+  SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  SurfaceId c_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+
+  auto e_hit_test_data = mojom::HitTestRegionList::New();
+  e_hit_test_data->surface_id = e_surface_id;
+  e_hit_test_data->flags = mojom::kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_div = mojom::HitTestRegion::New();
+  e_hit_test_region_div->flags = mojom::kHitTestMine;
+  e_hit_test_region_div->surface_id = e_surface_id;
+  e_hit_test_region_div->rect.SetRect(200, 200, 300, 200);
+
+  auto e_hit_test_region_c = mojom::HitTestRegion::New();
+  e_hit_test_region_c->flags = mojom::kHitTestChildSurface;
+  e_hit_test_region_c->surface_id = c_surface_id;
+  e_hit_test_region_c->rect.SetRect(100, 100, 200, 500);
+
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_c));
+  e_hit_test_data->regions.push_back(std::move(e_hit_test_region_div));
+
+  auto c_hit_test_data = mojom::HitTestRegionList::New();
+  c_hit_test_data->surface_id = c_surface_id;
+  c_hit_test_data->flags = mojom::kHitTestMine;
+  c_hit_test_data->bounds.SetRect(0, 0, 200, 500);
+
+  EXPECT_EQ(0, aggregator_.GetActiveRegionCount());
+
+  // Submit in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(c_hit_test_data));
+  EXPECT_EQ(1, aggregator_.GetPendingCount());
+
+  aggregator_.SubmitHitTestRegionList(std::move(e_hit_test_data));
+  EXPECT_EQ(2, aggregator_.GetPendingCount());
+
+  EXPECT_EQ(0, aggregator_.GetActiveRegionCount());
+
+  // Surfaces added to DisplayFrame in unexpected order.
+
+  EXPECT_EQ(0, aggregator_.Count());
+  EXPECT_EQ(0, aggregator_.GetActiveCount());
+
+  aggregator_.CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(1, aggregator_.GetActiveCount());
+  EXPECT_EQ(2, aggregator_.GetActiveRegionCount());
+
+  aggregator_.CallOnSurfaceWillDraw(c_surface_id);
+  EXPECT_EQ(2, aggregator_.GetActiveCount());
+  EXPECT_EQ(2, aggregator_.GetActiveRegionCount());
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(0, aggregator_.Count());
+  EXPECT_EQ(2, aggregator_.GetActiveRegionCount());
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(3, aggregator_.Count());
+  EXPECT_EQ(2, aggregator_.GetActiveRegionCount());
+
+  // Discard Surface and ensure active count goes down.
+
+  aggregator_.CallOnSurfaceDiscarded(c_surface_id);
+  EXPECT_EQ(2, aggregator_.GetActiveRegionCount());
+
+  aggregator_.CallOnSurfaceDiscarded(e_surface_id);
+  EXPECT_EQ(0, aggregator_.GetActiveRegionCount());
+}
+
+}  // namespace viz