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 "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 "display_hit_test_data_factory_local.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()
+      : aggregator_(
+            base::MakeUnique<hit_test::DisplayHitTestDataFactoryLocal>()) {}
+  ~HitTestAggregatorTest() override {}
+
+  void SetUp() override { Reset(); }
+
+  void TearDown() override { Reset(); }
+
+  HitTestAggregator aggregator_;
+
+  int count() {
+    DisplayHitTestRegion* start = aggregator_.GetCurrentRegions();
+    DisplayHitTestRegion* end = start;
+    while (end->child_count != kEndOfList) {
+      end++;
+    }
+    int count = end - start;
+    return count;
+  }
+
+  DisplayHitTestRegion* RegionAtIndex(int i) {
+    return aggregator_.GetCurrentRegions() + i;
+  }
+
+  int GetPendingCount() { return aggregator_.pending_.size(); }
+  int GetActiveCount() { return aggregator_.active_.size(); }
+
+  int GetPendingRegionCount() { return RegionCount(aggregator_.pending_); }
+  int GetActiveRegionCount() { return RegionCount(aggregator_.active_); }
+
+  void CallOnSurfaceWillDraw(cc::SurfaceId surface_id) {
+    aggregator_.OnSurfaceWillDraw(surface_id);
+  }
+
+  int RegionCount(const HitTestDataMap& map) {
+    int size = 0;
+    for (auto const& it : map) {
+      hit_test::mojom::HitTestData* hit_test_data = it.second.get();
+      size += hit_test_data->regions.size();
+    }
+    return size;
+  }
+
+  void Reset() {
+    aggregator_.read_display_hit_test_data_->regions[0].child_count =
+        kEndOfList;
+    aggregator_.write_display_hit_test_data_->regions[0].child_count =
+        kEndOfList;
+
+    aggregator_.pending_.clear();
+    aggregator_.active_.clear();
+  }
+
+  int GetDisplayHitTestDataSize() {
+    return aggregator_.read_display_hit_test_data_->size;
+  }
+
+  // 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 ( also matches the count ).
+  int CreateAndSubmitHitTestDataWith8Children(int id, int depth) {
+    cc::SurfaceId surface_id = MakeSurfaceId(kDisplayFrameSink, id);
+    id++;
+
+    auto hit_test_data = HitTestData::New();
+    hit_test_data->surface_id = surface_id;
+    hit_test_data->flags = kHitTestMine;
+    hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+    for (int i = 0; i < 8; i++) {
+      auto hit_test_region = HitTestRegion::New();
+      hit_test_region->rect.SetRect(100, 100, 100, 100);
+
+      if (depth > 0) {
+        hit_test_region->flags = kHitTestChildSurface;
+        hit_test_region->surface_id = MakeSurfaceId(kDisplayFrameSink, id);
+        id = CreateAndSubmitHitTestDataWith8Children(id, depth - 1);
+      } else {
+        hit_test_region->flags = kHitTestMine;
+      }
+      hit_test_data->regions.push_back(std::move(hit_test_region));
+    }
+
+    aggregator_.SubmitHitTestData(std::move(hit_test_data));
+    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(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->flags = kHitTestMine;
+  hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  aggregator_.SubmitHitTestData(std::move(hit_test_data));
+  EXPECT_EQ(count(), 0);
+
+  EXPECT_EQ(GetPendingCount(), 1);
+  EXPECT_EQ(GetActiveCount(), 0);
+
+  CallOnSurfaceWillDraw(display_surface_id);
+
+  EXPECT_EQ(GetPendingCount(), 0);
+  EXPECT_EQ(GetActiveCount(), 1);
+
+  aggregator_.Aggregate(display_surface_id);
+  aggregator_.Swap();
+
+  // Expect 1 entry routing all events to the one surface ( display root ).
+  EXPECT_EQ(count(), 1);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_EQ(region->flags, kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, display_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(0, 0, 1024, 768));
+  EXPECT_EQ(region->child_count, 0);
+}
+
+// One opaque embedder with two regions.
+//
+//  +e-------------+
+//  | +r1-+ +r2--+ |
+//  | |   | |    | |
+//  | |   | |    | |
+//  | +---+ +----+ |
+//  +--------------+
+//
+TEST_F(HitTestAggregatorTest, OneEmbedderTwoRegions) {
+  EXPECT_EQ(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->flags = kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_r1 = HitTestRegion::New();
+  e_hit_test_region_r1->flags = kHitTestMine;
+  e_hit_test_region_r1->rect.SetRect(100, 100, 200, 400);
+
+  auto e_hit_test_region_r2 = HitTestRegion::New();
+  e_hit_test_region_r2->flags = 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 HitTestData.
+
+  EXPECT_EQ(GetPendingCount(), 0);
+
+  aggregator_.SubmitHitTestData(std::move(e_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 1);
+
+  // Add Surfaces to DisplayFrame ( in unexpected order ).
+
+  EXPECT_EQ(count(), 0);
+  EXPECT_EQ(GetActiveCount(), 0);
+
+  CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(GetActiveCount(), 1);
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(count(), 0);
+
+  aggregator_.Swap();
+  EXPECT_EQ(count(), 3);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_EQ(region->flags, kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, e_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(0, 0, 1024, 768));
+  EXPECT_EQ(region->child_count, 2);
+
+  region = RegionAtIndex(1);
+  EXPECT_EQ(region->flags, kHitTestMine);
+  EXPECT_EQ(region->rect, gfx::Rect(100, 100, 200, 400));
+  EXPECT_EQ(region->child_count, 0);
+
+  region = RegionAtIndex(2);
+  EXPECT_EQ(region->flags, kHitTestMine);
+  EXPECT_EQ(region->rect, gfx::Rect(400, 100, 300, 400));
+  EXPECT_EQ(region->child_count, 0);
+}
+
+// One embedder with two children.
+//
+//  +e-------------+
+//  | +c1-+ +c2--+ |
+//  | |   | |    | |
+//  | |   | |    | |
+//  | +---+ +----+ |
+//  +--------------+
+//
+
+TEST_F(HitTestAggregatorTest, OneEmbedderTwoChildren) {
+  EXPECT_EQ(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->flags = kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_c1 = HitTestRegion::New();
+  e_hit_test_region_c1->flags = 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 = HitTestRegion::New();
+  e_hit_test_region_c2->flags = 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 = HitTestData::New();
+  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_EQ(GetPendingCount(), 0);
+
+  aggregator_.SubmitHitTestData(std::move(c1_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 1);
+
+  aggregator_.SubmitHitTestData(std::move(e_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 2);
+
+  aggregator_.SubmitHitTestData(std::move(c2_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 3);
+
+  // Surfaces added to DisplayFrame ( in unexpected order ).
+
+  EXPECT_EQ(count(), 0);
+
+  EXPECT_EQ(GetActiveCount(), 0);
+
+  CallOnSurfaceWillDraw(c2_surface_id);
+  EXPECT_EQ(GetActiveCount(), 1);
+
+  CallOnSurfaceWillDraw(c1_surface_id);
+  EXPECT_EQ(GetActiveCount(), 2);
+
+  CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(GetActiveCount(), 3);
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(count(), 0);
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(count(), 3);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_EQ(region->flags, kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, e_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(0, 0, 1024, 768));
+  EXPECT_EQ(region->child_count, 2);
+
+  region = RegionAtIndex(1);
+  EXPECT_EQ(region->flags, kHitTestChildSurface);
+  EXPECT_EQ(region->frame_sink_id, c1_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(100, 100, 200, 300));
+  EXPECT_EQ(region->child_count, 0);
+
+  region = RegionAtIndex(2);
+  EXPECT_EQ(region->flags, kHitTestChildSurface);
+  EXPECT_EQ(region->frame_sink_id, c2_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(400, 100, 400, 300));
+  EXPECT_EQ(region->child_count, 0);
+}
+
+// Occluded child frame ( OOPIF ).
+//
+//  +e-----------+
+//  | +c--+      |
+//  | | +div-+   |
+//  | | |    |   |
+//  | | +----+   |
+//  | +---+      |
+//  +------------+
+//
+
+TEST_F(HitTestAggregatorTest, OccludedChildFrame) {
+  EXPECT_EQ(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->flags = kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_div = HitTestRegion::New();
+  e_hit_test_region_div->flags = 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 = HitTestRegion::New();
+  e_hit_test_region_c->flags = 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 = HitTestData::New();
+  c_hit_test_data->surface_id = c_surface_id;
+  c_hit_test_data->flags = kHitTestMine;
+  c_hit_test_data->bounds.SetRect(0, 0, 200, 500);
+
+  // Submit ( in unexpected order ).
+
+  EXPECT_EQ(GetPendingCount(), 0);
+
+  aggregator_.SubmitHitTestData(std::move(c_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 1);
+
+  aggregator_.SubmitHitTestData(std::move(e_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 2);
+
+  // Surfaces added to DisplayFrame ( in unexpected order ).
+
+  EXPECT_EQ(count(), 0);
+
+  EXPECT_EQ(GetActiveCount(), 0);
+
+  CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(GetActiveCount(), 1);
+
+  CallOnSurfaceWillDraw(c_surface_id);
+  EXPECT_EQ(GetActiveCount(), 2);
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(count(), 0);
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(count(), 3);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_EQ(region->flags, kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, e_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(0, 0, 1024, 768));
+  EXPECT_EQ(region->child_count, 2);
+
+  region = RegionAtIndex(1);
+  EXPECT_EQ(region->flags, kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, e_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(200, 200, 300, 200));
+  EXPECT_EQ(region->child_count, 0);
+
+  region = RegionAtIndex(2);
+  EXPECT_EQ(region->flags, kHitTestChildSurface | kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, c_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(100, 100, 200, 500));
+  EXPECT_EQ(region->child_count, 0);
+}
+
+// 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(count(), 0);
+
+  cc::SurfaceId e_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+  cc::SurfaceId c_surface_id = MakeSurfaceId(kDisplayFrameSink, 2);
+  cc::SurfaceId a_surface_id = MakeSurfaceId(kDisplayFrameSink, 3);
+  cc::SurfaceId b_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->flags = kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_c = HitTestRegion::New();
+  e_hit_test_region_c->flags = 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 = HitTestData::New();
+  c_hit_test_data->surface_id = c_surface_id;
+  c_hit_test_data->flags = kHitTestIgnore;
+  c_hit_test_data->bounds.SetRect(0, 0, 1600, 800);
+
+  auto c_hit_test_region_a = HitTestRegion::New();
+  c_hit_test_region_a->flags = 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 = HitTestRegion::New();
+  c_hit_test_region_b->flags = 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 = HitTestData::New();
+  a_hit_test_data->surface_id = a_surface_id;
+  a_hit_test_data->flags = kHitTestMine;
+  a_hit_test_data->bounds.SetRect(0, 0, 200, 100);
+
+  auto b_hit_test_data = HitTestData::New();
+  b_hit_test_data->surface_id = b_surface_id;
+  b_hit_test_data->flags = kHitTestMine;
+  b_hit_test_data->bounds.SetRect(0, 100, 800, 600);
+
+  // Submit ( in unexpected order ).
+
+  EXPECT_EQ(GetPendingCount(), 0);
+
+  aggregator_.SubmitHitTestData(std::move(c_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 1);
+
+  aggregator_.SubmitHitTestData(std::move(a_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 2);
+
+  aggregator_.SubmitHitTestData(std::move(b_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 3);
+
+  aggregator_.SubmitHitTestData(std::move(e_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 4);
+
+  // Surfaces added to DisplayFrame ( in unexpected order ).
+
+  EXPECT_EQ(count(), 0);
+
+  EXPECT_EQ(GetActiveCount(), 0);
+
+  CallOnSurfaceWillDraw(c_surface_id);
+  EXPECT_EQ(GetActiveCount(), 1);
+
+  CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(GetActiveCount(), 2);
+
+  CallOnSurfaceWillDraw(b_surface_id);
+  EXPECT_EQ(GetActiveCount(), 3);
+
+  CallOnSurfaceWillDraw(a_surface_id);
+  EXPECT_EQ(GetActiveCount(), 4);
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(count(), 0);
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(count(), 4);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_EQ(region->flags, kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, e_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(0, 0, 1024, 768));
+  EXPECT_EQ(region->child_count, 3);
+
+  region = RegionAtIndex(1);
+  EXPECT_EQ(region->flags, kHitTestChildSurface | kHitTestIgnore);
+  EXPECT_EQ(region->frame_sink_id, c_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(200, 100, 1600, 800));
+  EXPECT_EQ(region->child_count, 2);
+
+  gfx::Point point(300, 300);
+  region->transform.TransformPointReverse(&point);
+  EXPECT_TRUE(point == gfx::Point(100, 200));
+
+  region = RegionAtIndex(2);
+  EXPECT_EQ(region->flags, kHitTestChildSurface | kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, a_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(0, 0, 200, 100));
+  EXPECT_EQ(region->child_count, 0);
+
+  region = RegionAtIndex(3);
+  EXPECT_EQ(region->flags, kHitTestChildSurface | kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, b_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(0, 100, 800, 600));
+  EXPECT_EQ(region->child_count, 0);
+}
+
+// Three children deep.
+//
+//  +e------------+
+//  | +c1-------+ |
+//  | | +c2---+ | |
+//  | | | +c3-| | |
+//  | | | |   | | |
+//  | | | +---| | |
+//  | | +-----+ | |
+//  | +---------+ |
+//  +-------------+
+//
+
+TEST_F(HitTestAggregatorTest, ThreeChildrenDeep) {
+  EXPECT_EQ(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->flags = kHitTestMine;
+  e_hit_test_data->bounds.SetRect(0, 0, 1024, 768);
+
+  auto e_hit_test_region_c1 = HitTestRegion::New();
+  e_hit_test_region_c1->flags = 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 = HitTestData::New();
+  c1_hit_test_data->surface_id = c1_surface_id;
+  c1_hit_test_data->flags = kHitTestMine;
+  c1_hit_test_data->bounds.SetRect(0, 0, 600, 600);
+
+  auto c1_hit_test_region_c2 = HitTestRegion::New();
+  c1_hit_test_region_c2->flags = 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 = HitTestData::New();
+  c2_hit_test_data->surface_id = c2_surface_id;
+  c2_hit_test_data->flags = kHitTestMine;
+  c2_hit_test_data->bounds.SetRect(0, 0, 400, 400);
+
+  auto c2_hit_test_region_c3 = HitTestRegion::New();
+  c2_hit_test_region_c3->flags = 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 = HitTestData::New();
+  c3_hit_test_data->surface_id = c3_surface_id;
+  c3_hit_test_data->flags = kHitTestMine;
+  c3_hit_test_data->bounds.SetRect(0, 0, 200, 200);
+
+  // Submit ( in unexpected order ).
+
+  EXPECT_EQ(GetPendingCount(), 0);
+
+  aggregator_.SubmitHitTestData(std::move(c1_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 1);
+
+  aggregator_.SubmitHitTestData(std::move(c3_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 2);
+
+  aggregator_.SubmitHitTestData(std::move(e_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 3);
+
+  aggregator_.SubmitHitTestData(std::move(c2_hit_test_data));
+  EXPECT_EQ(GetPendingCount(), 4);
+
+  // Surfaces added to DisplayFrame ( in unexpected order ).
+
+  EXPECT_EQ(count(), 0);
+
+  EXPECT_EQ(GetActiveCount(), 0);
+
+  CallOnSurfaceWillDraw(c2_surface_id);
+  EXPECT_EQ(GetActiveCount(), 1);
+
+  CallOnSurfaceWillDraw(c1_surface_id);
+  EXPECT_EQ(GetActiveCount(), 2);
+
+  CallOnSurfaceWillDraw(e_surface_id);
+  EXPECT_EQ(GetActiveCount(), 3);
+
+  CallOnSurfaceWillDraw(c3_surface_id);
+  EXPECT_EQ(GetActiveCount(), 4);
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(e_surface_id);
+  EXPECT_EQ(count(), 0);
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(count(), 4);
+
+  DisplayHitTestRegion* region;
+
+  region = RegionAtIndex(0);
+  EXPECT_EQ(region->flags, kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, e_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(0, 0, 1024, 768));
+  EXPECT_EQ(region->child_count, 3);
+
+  region = RegionAtIndex(1);
+  EXPECT_EQ(region->flags, kHitTestChildSurface | kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, c1_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(100, 100, 700, 700));
+  EXPECT_EQ(region->child_count, 2);
+
+  region = RegionAtIndex(2);
+  EXPECT_EQ(region->flags, kHitTestChildSurface | kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, c2_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(100, 100, 500, 500));
+  EXPECT_EQ(region->child_count, 1);
+
+  region = RegionAtIndex(3);
+  EXPECT_EQ(region->flags, kHitTestChildSurface | kHitTestMine);
+  EXPECT_EQ(region->frame_sink_id, c3_surface_id.frame_sink_id());
+  EXPECT_EQ(region->rect, gfx::Rect(100, 100, 300, 300));
+  EXPECT_EQ(region->child_count, 0);
+}
+
+// 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(count(), 0);
+
+  EXPECT_LT(GetDisplayHitTestDataSize(), 4096);
+
+  cc::SurfaceId display_surface_id = MakeSurfaceId(kDisplayFrameSink, 1);
+
+  int next_surface_id = CreateAndSubmitHitTestDataWith8Children(1, 3);
+  int surface_count = next_surface_id - 1;
+
+  int region_count = GetPendingRegionCount();
+
+  // Expect 4680 regions:
+  //  8 children 4 levels deep 8*8*8*8 is  4096
+  //  1 region for each embedder/surface +  584
+  //                                      -----
+  //                                       4680.
+  EXPECT_EQ(region_count, 4680);
+
+  EXPECT_EQ(GetPendingCount(), surface_count);
+
+  // Mark Surfaces as added to DisplayFrame ( in unexpected order ).
+
+  EXPECT_EQ(count(), 0);
+  EXPECT_EQ(GetActiveCount(), 0);
+
+  for (int i = 1; i <= surface_count; i++) {
+    cc::SurfaceId surface_id = MakeSurfaceId(kDisplayFrameSink, i);
+    CallOnSurfaceWillDraw(surface_id);
+  }
+
+  EXPECT_EQ(GetActiveCount(), surface_count);
+
+  // Aggregate and swap.
+
+  aggregator_.Aggregate(display_surface_id);
+  EXPECT_EQ(count(), 0);
+
+  aggregator_.Swap();
+
+  EXPECT_EQ(count(), region_count + 1);
+
+  EXPECT_GE(GetDisplayHitTestDataSize(), region_count);
+}
+
+}  // namespace test
+}  // namespace hit_test
+}  // namespace viz