Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

9 files changed, 2102 insertions, 0 deletions

diff --git a/widget/tests/gtest/MockWinWidget.cpp b/widget/tests/gtest/MockWinWidget.cpp
new file mode 100644
index 0000000000..ed7850076f
--- /dev/null
+++ b/widget/tests/gtest/MockWinWidget.cpp
@@ -0,0 +1,77 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "MockWinWidget.h"
+
+#include "mozilla/gfx/Logging.h"
+
+NS_IMPL_ISUPPORTS_INHERITED0(MockWinWidget, nsBaseWidget)
+
+// static
+RefPtr<MockWinWidget> MockWinWidget::Create(DWORD aStyle, DWORD aExStyle,
+                                            const LayoutDeviceIntRect& aRect) {
+  RefPtr<MockWinWidget> window = new MockWinWidget;
+  if (!window->Initialize(aStyle, aExStyle, aRect)) {
+    return nullptr;
+  }
+
+  return window;
+}
+
+MockWinWidget::MockWinWidget() {}
+
+MockWinWidget::~MockWinWidget() {
+  if (mWnd) {
+    ::DestroyWindow(mWnd);
+    mWnd = 0;
+  }
+}
+
+bool MockWinWidget::Initialize(DWORD aStyle, DWORD aExStyle,
+                               const LayoutDeviceIntRect& aRect) {
+  WNDCLASSW wc;
+  const wchar_t className[] = L"MozillaMockWinWidget";
+  HMODULE hSelf = ::GetModuleHandle(nullptr);
+
+  if (!GetClassInfoW(hSelf, className, &wc)) {
+    ZeroMemory(&wc, sizeof(WNDCLASSW));
+    wc.hInstance = hSelf;
+    wc.lpfnWndProc = ::DefWindowProc;
+    wc.lpszClassName = className;
+    RegisterClassW(&wc);
+  }
+
+  mWnd = ::CreateWindowExW(aExStyle, className, className, aStyle, aRect.X(),
+                           aRect.Y(), aRect.Width(), aRect.Height(), nullptr,
+                           nullptr, hSelf, nullptr);
+  if (!mWnd) {
+    gfxCriticalNoteOnce << "GetClientRect failed " << ::GetLastError();
+    return false;
+  }
+
+  // First nccalcszie (during CreateWindow) for captioned windows is
+  // deliberately ignored so force a second one here to get the right
+  // non-client set up.
+  if (mWnd && (aStyle & WS_CAPTION)) {
+    ::SetWindowPos(mWnd, NULL, 0, 0, 0, 0,
+                   SWP_FRAMECHANGED | SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER |
+                       SWP_NOACTIVATE | SWP_NOREDRAW);
+  }
+
+  mBounds = aRect;
+  return true;
+}
+
+void MockWinWidget::NotifyOcclusionState(
+    mozilla::widget::OcclusionState aState) {
+  mCurrentState = aState;
+}
+
+nsSizeMode MockWinWidget::SizeMode() {
+  if (::IsIconic(mWnd)) {
+    return nsSizeMode_Minimized;
+  }
+  return nsSizeMode_Normal;
+}
diff --git a/widget/tests/gtest/MockWinWidget.h b/widget/tests/gtest/MockWinWidget.h
new file mode 100644
index 0000000000..891e1c942d
--- /dev/null
+++ b/widget/tests/gtest/MockWinWidget.h
@@ -0,0 +1,85 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef GTEST_MockWinWidget_H
+#define GTEST_MockWinWidget_H
+
+#include <windows.h>
+
+#include "nsBaseWidget.h"
+#include "Units.h"
+
+class MockWinWidget : public nsBaseWidget {
+ public:
+  static RefPtr<MockWinWidget> Create(DWORD aStyle, DWORD aExStyle,
+                                      const LayoutDeviceIntRect& aRect);
+
+  NS_DECL_ISUPPORTS_INHERITED
+
+  void NotifyOcclusionState(mozilla::widget::OcclusionState aState) override;
+
+  void SetExpectation(mozilla::widget::OcclusionState aExpectation) {
+    mExpectation = aExpectation;
+  }
+
+  bool IsExpectingCall() const { return mExpectation != mCurrentState; }
+
+  HWND GetWnd() { return mWnd; }
+
+  nsSizeMode SizeMode() override;
+  void SetSizeMode(nsSizeMode aMode) override {}
+
+  void* GetNativeData(uint32_t aDataType) override { return nullptr; }
+
+  virtual nsresult Create(nsIWidget* aParent, nsNativeWidget aNativeParent,
+                          const LayoutDeviceIntRect& aRect,
+                          InitData* aInitData = nullptr) override {
+    return NS_OK;
+  }
+  virtual nsresult Create(nsIWidget* aParent, nsNativeWidget aNativeParent,
+                          const DesktopIntRect& aRect,
+                          InitData* aInitData = nullptr) override {
+    return NS_OK;
+  }
+  virtual void Show(bool aState) override {}
+  virtual bool IsVisible() const override { return true; }
+  virtual void Move(double aX, double aY) override {}
+  virtual void Resize(double aWidth, double aHeight, bool aRepaint) override {}
+  virtual void Resize(double aX, double aY, double aWidth, double aHeight,
+                      bool aRepaint) override {}
+
+  virtual void Enable(bool aState) override {}
+  virtual bool IsEnabled() const override { return true; }
+  virtual void SetFocus(Raise, mozilla::dom::CallerType aCallerType) override {}
+  virtual void Invalidate(const LayoutDeviceIntRect& aRect) override {}
+  virtual nsresult SetTitle(const nsAString& title) override { return NS_OK; }
+  virtual LayoutDeviceIntPoint WidgetToScreenOffset() override {
+    return LayoutDeviceIntPoint(0, 0);
+  }
+  virtual nsresult DispatchEvent(mozilla::WidgetGUIEvent* aEvent,
+                                 nsEventStatus& aStatus) override {
+    return NS_OK;
+  }
+  virtual void SetInputContext(const InputContext& aContext,
+                               const InputContextAction& aAction) override {}
+  virtual InputContext GetInputContext() override { abort(); }
+
+ private:
+  MockWinWidget();
+  ~MockWinWidget();
+
+  bool Initialize(DWORD aStyle, DWORD aExStyle,
+                  const LayoutDeviceIntRect& aRect);
+
+  HWND mWnd = 0;
+
+  mozilla::widget::OcclusionState mExpectation =
+      mozilla::widget::OcclusionState::UNKNOWN;
+  mozilla::widget::OcclusionState mCurrentState =
+      mozilla::widget::OcclusionState::UNKNOWN;
+};
+
+#endif
diff --git a/widget/tests/gtest/TestTimeConverter.cpp b/widget/tests/gtest/TestTimeConverter.cpp
new file mode 100644
index 0000000000..22cbc3f9e6
--- /dev/null
+++ b/widget/tests/gtest/TestTimeConverter.cpp
@@ -0,0 +1,265 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+#include "mozilla/TimeStamp.h"
+#include "SystemTimeConverter.h"
+
+using mozilla::SystemTimeConverter;
+using mozilla::TimeDuration;
+using mozilla::TimeStamp;
+
+namespace {
+
+// This class provides a mock implementation of the CurrentTimeGetter template
+// type used in SystemTimeConverter. It can be constructed with a particular
+// Time and always returns that Time.
+template <typename Time>
+class MockCurrentTimeGetter {
+ public:
+  MockCurrentTimeGetter() : mTime(0) {}
+  explicit MockCurrentTimeGetter(Time aTime) : mTime(aTime) {}
+
+  // Methods needed for CurrentTimeGetter compatibility
+  Time GetCurrentTime() const { return mTime; }
+  void GetTimeAsyncForPossibleBackwardsSkew(const TimeStamp& aNow) {}
+
+ private:
+  Time mTime;
+};
+
+// This is another mock implementation of the CurrentTimeGetter template
+// type used in SystemTimeConverter, except this asserts that it will not be
+// used. i.e. it should only be used in calls to SystemTimeConverter that we
+// know will not invoke it.
+template <typename Time>
+class UnusedCurrentTimeGetter {
+ public:
+  Time GetCurrentTime() const {
+    EXPECT_TRUE(false);
+    return 0;
+  }
+
+  void GetTimeAsyncForPossibleBackwardsSkew(const TimeStamp& aNow) {
+    EXPECT_TRUE(false);
+  }
+};
+
+// This class provides a mock implementation of the TimeStampNowProvider
+// template type used in SystemTimeConverter. It also has other things in it
+// that allow the test to better control time for testing purposes.
+class MockTimeStamp {
+ public:
+  // This should generally be called at the start of every test function, as
+  // it will initialize this class's static fields to sane values. In particular
+  // it will initialize the baseline TimeStamp against which all other
+  // TimeStamps are compared.
+  static void Init() {
+    sBaseline = TimeStamp::Now();
+    sTimeStamp = sBaseline;
+  }
+
+  // Advance the timestamp returned by `MockTimeStamp::Now()`
+  static void Advance(double ms) {
+    sTimeStamp += TimeDuration::FromMilliseconds(ms);
+  }
+
+  // Returns the baseline TimeStamp, that is used as a fixed reference point
+  // in time against which other TimeStamps can be compared. This is needed
+  // because mozilla::TimeStamp itself doesn't provide any conversion to
+  // human-readable strings, and we need to convert it to a TimeDuration in
+  // order to get that. This baseline TimeStamp can be used to turn an
+  // arbitrary TimeStamp into a TimeDuration.
+  static TimeStamp Baseline() { return sBaseline; }
+
+  // This is the method needed for TimeStampNowProvider compatibility, and
+  // simulates `TimeStamp::Now()`
+  static TimeStamp Now() { return sTimeStamp; }
+
+ private:
+  static TimeStamp sTimeStamp;
+  static TimeStamp sBaseline;
+};
+
+TimeStamp MockTimeStamp::sTimeStamp;
+TimeStamp MockTimeStamp::sBaseline;
+
+// Could have platform-specific implementations of this using DWORD, guint32,
+// etc behind ifdefs. But this is sufficient for now.
+using GTestTime = uint32_t;
+using TimeConverter = SystemTimeConverter<GTestTime, MockTimeStamp>;
+
+}  // namespace
+
+// Checks the expectation that the TimeStamp `ts` is exactly `ms` milliseconds
+// after the baseline timestamp. This is a macro so gtest still gives us useful
+// line numbers for failures.
+#define EXPECT_TS(ts, ms) \
+  EXPECT_EQ((ts)-MockTimeStamp::Baseline(), TimeDuration::FromMilliseconds(ms))
+
+#define EXPECT_TS_FUZZY(ts, ms) \
+  EXPECT_DOUBLE_EQ(((ts)-MockTimeStamp::Baseline()).ToMilliseconds(), ms)
+
+TEST(TimeConverter, SanityCheck)
+{
+  MockTimeStamp::Init();
+
+  MockCurrentTimeGetter timeGetter(10);
+  UnusedCurrentTimeGetter<GTestTime> unused;
+  TimeConverter converter;
+
+  // This call sets the reference time and timestamp
+  TimeStamp ts = converter.GetTimeStampFromSystemTime(10, timeGetter);
+  EXPECT_TS(ts, 0);
+
+  // Advance "TimeStamp::Now" by 10ms, use the same event time and OS time.
+  // Since the event time is the same as before, we expect to get back the
+  // same TimeStamp as before too, despite Now() changing.
+  MockTimeStamp::Advance(10);
+  ts = converter.GetTimeStampFromSystemTime(10, unused);
+  EXPECT_TS(ts, 0);
+
+  // Now let's use an event time 20ms after the old event. This will trigger
+  // forward skew detection and resync the TimeStamp for the new event to Now().
+  ts = converter.GetTimeStampFromSystemTime(30, unused);
+  EXPECT_TS(ts, 10);
+}
+
+TEST(TimeConverter, Overflow)
+{
+  // This tests wrapping time around the max value supported in the GTestTime
+  // type and ensuring it is handled properly.
+
+  MockTimeStamp::Init();
+
+  const GTestTime max = std::numeric_limits<GTestTime>::max();
+  const GTestTime min = std::numeric_limits<GTestTime>::min();
+  double fullRange = (double)max - (double)min;
+  double wrapPeriod = fullRange + 1.0;
+
+  GTestTime almostOverflowed = max - 100;
+  GTestTime overflowed = max + 100;
+  MockCurrentTimeGetter timeGetter(almostOverflowed);
+  UnusedCurrentTimeGetter<GTestTime> unused;
+  TimeConverter converter;
+
+  // Set reference time to 100ms before the overflow point
+  TimeStamp ts =
+      converter.GetTimeStampFromSystemTime(almostOverflowed, timeGetter);
+  EXPECT_TS(ts, 0);
+
+  // Advance everything by 200ms and verify we get back a TimeStamp 200ms from
+  // the baseline despite wrapping an overflow.
+  MockTimeStamp::Advance(200);
+  ts = converter.GetTimeStampFromSystemTime(overflowed, unused);
+  EXPECT_TS(ts, 200);
+
+  // Advance by another full wraparound of the time. This loses some precision
+  // so we have to do the FUZZY match
+  MockTimeStamp::Advance(wrapPeriod);
+  ts = converter.GetTimeStampFromSystemTime(overflowed, unused);
+  EXPECT_TS_FUZZY(ts, 200.0 + wrapPeriod);
+}
+
+TEST(TimeConverter, InvertedOverflow)
+{
+  // This tests time going from near the min value of GTestTime to the max
+  // value of GTestTime
+
+  MockTimeStamp::Init();
+
+  const GTestTime max = std::numeric_limits<GTestTime>::max();
+  const GTestTime min = std::numeric_limits<GTestTime>::min();
+  double fullRange = (double)max - (double)min;
+  double wrapPeriod = fullRange + 1.0;
+
+  GTestTime nearRangeMin = min + 100;
+  GTestTime nearRangeMax = max - 100;
+  double gap = (double)nearRangeMax - (double)nearRangeMin;
+
+  MockCurrentTimeGetter timeGetter(nearRangeMin);
+  UnusedCurrentTimeGetter<GTestTime> unused;
+  TimeConverter converter;
+
+  // Set reference time to value near min numeric limit
+  TimeStamp ts = converter.GetTimeStampFromSystemTime(nearRangeMin, timeGetter);
+  EXPECT_TS(ts, 0);
+
+  // Advance to value near max numeric limit
+  MockTimeStamp::Advance(gap);
+  ts = converter.GetTimeStampFromSystemTime(nearRangeMax, unused);
+  EXPECT_TS(ts, gap);
+
+  // Advance by another full wraparound of the time. This loses some precision
+  // so we have to do the FUZZY match
+  MockTimeStamp::Advance(wrapPeriod);
+  ts = converter.GetTimeStampFromSystemTime(nearRangeMax, unused);
+  EXPECT_TS_FUZZY(ts, gap + wrapPeriod);
+}
+
+TEST(TimeConverter, HalfRangeBoundary)
+{
+  MockTimeStamp::Init();
+
+  GTestTime max = std::numeric_limits<GTestTime>::max();
+  GTestTime min = std::numeric_limits<GTestTime>::min();
+  double fullRange = (double)max - (double)min;
+  double wrapPeriod = fullRange + 1.0;
+  GTestTime halfRange = (GTestTime)(fullRange / 2.0);
+  GTestTime halfWrapPeriod = (GTestTime)(wrapPeriod / 2.0);
+
+  TimeConverter converter;
+
+  GTestTime firstEvent = 10;
+  MockCurrentTimeGetter timeGetter(firstEvent);
+  UnusedCurrentTimeGetter<GTestTime> unused;
+
+  // Set reference time
+  TimeStamp ts = converter.GetTimeStampFromSystemTime(firstEvent, timeGetter);
+  EXPECT_TS(ts, 0);
+
+  // Advance event time by just under the half-period, to trigger about as big
+  // a forwards skew as we possibly can.
+  GTestTime secondEvent = firstEvent + (halfWrapPeriod - 1);
+  ts = converter.GetTimeStampFromSystemTime(secondEvent, unused);
+  EXPECT_TS(ts, 0);
+
+  // The above forwards skew will have reset the reference timestamp. Now
+  // advance Now time by just under the half-range, to trigger about as big
+  // a backwards skew as we possibly can.
+  MockTimeStamp::Advance(halfRange - 1);
+  ts = converter.GetTimeStampFromSystemTime(secondEvent, unused);
+  EXPECT_TS(ts, 0);
+}
+
+TEST(TimeConverter, FractionalMillisBug1626734)
+{
+  MockTimeStamp::Init();
+
+  TimeConverter converter;
+
+  GTestTime eventTime = 10;
+  MockCurrentTimeGetter timeGetter(eventTime);
+  UnusedCurrentTimeGetter<GTestTime> unused;
+
+  TimeStamp ts = converter.GetTimeStampFromSystemTime(eventTime, timeGetter);
+  EXPECT_TS(ts, 0);
+
+  MockTimeStamp::Advance(0.2);
+  ts = converter.GetTimeStampFromSystemTime(eventTime, unused);
+  EXPECT_TS(ts, 0);
+
+  MockTimeStamp::Advance(0.9);
+  TimeStamp ts2 = converter.GetTimeStampFromSystemTime(eventTime, unused);
+  EXPECT_TS(ts2, 0);
+
+  // Since ts2 came from a "future" call relative to ts, we expect ts2 to not
+  // be "before" ts. (i.e. time shouldn't go backwards, even by fractional
+  // milliseconds). This assertion is technically already implied by the
+  // EXPECT_TS checks above, but fixing this assertion is the end result that
+  // we wanted in bug 1626734 so it feels appropriate to recheck it explicitly.
+  EXPECT_TRUE(ts <= ts2);
+}
diff --git a/widget/tests/gtest/TestTouchResampler.cpp b/widget/tests/gtest/TestTouchResampler.cpp
new file mode 100644
index 0000000000..1a5b8e2430
--- /dev/null
+++ b/widget/tests/gtest/TestTouchResampler.cpp
@@ -0,0 +1,941 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <initializer_list>
+#include "InputData.h"
+#include "Units.h"
+#include "gtest/gtest.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/TimeStamp.h"
+#include "TouchResampler.h"
+
+using namespace mozilla;
+using widget::TouchResampler;
+
+class TouchResamplerTest : public ::testing::Test {
+ protected:
+  virtual void SetUp() { baseTimeStamp = TimeStamp::Now(); }
+
+  TimeStamp Time(double aMilliseconds) {
+    return baseTimeStamp + TimeDuration::FromMilliseconds(aMilliseconds);
+  }
+
+  uint64_t ProcessEvent(
+      MultiTouchInput::MultiTouchType aType,
+      std::initializer_list<std::pair<TimeStamp, ScreenIntPoint>>
+          aHistoricalData,
+      const TimeStamp& aTimeStamp, const ScreenIntPoint& aPosition) {
+    MultiTouchInput input(aType, 0, aTimeStamp, 0);
+    input.mTouches.AppendElement(SingleTouchData(1, aPosition, {}, 0.0f, 0.0f));
+    for (const auto& histData : aHistoricalData) {
+      input.mTouches[0].mHistoricalData.AppendElement(
+          SingleTouchData::HistoricalTouchData{
+              histData.first, histData.second, {}, {}, 0.0f, 0.0f});
+    }
+    return resampler.ProcessEvent(std::move(input));
+  }
+
+  void CheckTime(const TimeStamp& aTimeStamp,
+                 const TimeStamp& aExpectedTimeStamp) {
+    EXPECT_EQ((aTimeStamp - baseTimeStamp).ToMilliseconds(),
+              (aExpectedTimeStamp - baseTimeStamp).ToMilliseconds());
+  }
+
+  void CheckEvent(const MultiTouchInput& aEvent,
+                  MultiTouchInput::MultiTouchType aExpectedType,
+                  std::initializer_list<std::pair<TimeStamp, ScreenIntPoint>>
+                      aExpectedHistoricalData,
+                  const TimeStamp& aExpectedTimeStamp,
+                  const ScreenIntPoint& aExpectedPosition) {
+    EXPECT_EQ(aEvent.mType, aExpectedType);
+    EXPECT_EQ(aEvent.mTouches.Length(), size_t(1));
+    EXPECT_EQ(aEvent.mTouches[0].mHistoricalData.Length(),
+              aExpectedHistoricalData.size());
+    for (size_t i = 0; i < aExpectedHistoricalData.size(); i++) {
+      CheckTime(aEvent.mTouches[0].mHistoricalData[i].mTimeStamp,
+                aExpectedHistoricalData.begin()[i].first);
+      EXPECT_EQ(aEvent.mTouches[0].mHistoricalData[i].mScreenPoint,
+                aExpectedHistoricalData.begin()[i].second);
+    }
+    CheckTime(aEvent.mTimeStamp, aExpectedTimeStamp);
+    EXPECT_EQ(aEvent.mTouches[0].mScreenPoint, aExpectedPosition);
+  }
+
+  struct ExpectedOutgoingEvent {
+    Maybe<uint64_t> mEventId;
+    MultiTouchInput::MultiTouchType mType = MultiTouchInput::MULTITOUCH_START;
+    std::initializer_list<std::pair<TimeStamp, ScreenIntPoint>> mHistoricalData;
+    TimeStamp mTimeStamp;
+    ScreenIntPoint mPosition;
+  };
+
+  void CheckOutgoingEvents(
+      std::initializer_list<ExpectedOutgoingEvent> aExpectedEvents) {
+    auto outgoing = resampler.ConsumeOutgoingEvents();
+    EXPECT_EQ(outgoing.size(), aExpectedEvents.size());
+    for (const auto& expectedEvent : aExpectedEvents) {
+      auto outgoingEvent = std::move(outgoing.front());
+      outgoing.pop();
+
+      EXPECT_EQ(outgoingEvent.mEventId, expectedEvent.mEventId);
+      CheckEvent(outgoingEvent.mEvent, expectedEvent.mType,
+                 expectedEvent.mHistoricalData, expectedEvent.mTimeStamp,
+                 expectedEvent.mPosition);
+    }
+  }
+
+  TimeStamp baseTimeStamp;
+  TouchResampler resampler;
+};
+
+TEST_F(TouchResamplerTest, BasicExtrapolation) {
+  // Execute the following sequence:
+  //
+  // 0----------10-------16-----20---------------32------------
+  // * touchstart at (10, 10)
+  //             * touchmove at (20, 20)
+  //                      * frame
+  //                             * touchend at (20, 20)
+  //                                              * frame
+  //
+  // And expect the following output:
+  //
+  // 0----------10-------16-----20---------------32------------
+  // * touchstart at (10, 10)
+  //                      * touchmove at (26, 26)
+  //                      * touchmove at (20, 20)
+  //                             * touchend at (20, 20)
+  //
+  // The first frame should emit an extrapolated touchmove from the position
+  // data in the touchstart and touchmove events.
+  // The touchend should force a synthesized touchmove that returns back to a
+  // non-resampled position.
+
+  EXPECT_FALSE(resampler.InTouchingState());
+
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(10, 10));
+  EXPECT_TRUE(resampler.InTouchingState());
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(10.0),
+                              ScreenIntPoint(20, 20));
+
+  resampler.NotifyFrame(Time(16.0));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(10, 10)},
+
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(10.0), ScreenIntPoint(20, 20)}},
+       Time(16.0),
+       ScreenIntPoint(26, 26)},
+  });
+
+  auto idEnd2 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(20.0),
+                             ScreenIntPoint(20, 20));
+
+  EXPECT_FALSE(resampler.InTouchingState());
+
+  CheckOutgoingEvents({
+      {Nothing(),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(16.0),
+       ScreenIntPoint(20, 20)},
+
+      {Some(idEnd2),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(20.0),
+       ScreenIntPoint(20, 20)},
+  });
+
+  // No more events should be produced from here on out.
+  resampler.NotifyFrame(Time(32.0));
+  auto outgoing = resampler.ConsumeOutgoingEvents();
+  EXPECT_TRUE(outgoing.empty());
+}
+
+TEST_F(TouchResamplerTest, BasicInterpolation) {
+  // Same test as BasicExtrapolation, but with a frame time that's 10ms earlier.
+  //
+  // Execute the following sequence:
+  //
+  // 0------6---10-----------20--22------------30-------------
+  // * touchstart at (10, 10)
+  //             * touchmove at (20, 20)
+  //        * frame
+  //                          * touchend at (20, 20)
+  //                              * frame
+  //
+  // And expect the following output:
+  //
+  // 0------6---10-----------20--22------------30-------------
+  // * touchstart at (10, 10)
+  //        * touchmove (16, 16)
+  //             * touchmove (20, 20)
+  //                          * touchend at (20, 20)
+  //
+  // The first frame should emit an interpolated touchmove from the position
+  // data in the touchstart and touchmove events.
+  // The touchend should create a touchmove that returns back to a non-resampled
+  // position.
+
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(10, 10));
+  EXPECT_TRUE(resampler.InTouchingState());
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(10.0),
+                              ScreenIntPoint(20, 20));
+
+  resampler.NotifyFrame(Time(6.0));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(10, 10)},
+
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(6.0),
+       ScreenIntPoint(16, 16)},
+  });
+
+  auto idEnd2 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(20.0),
+                             ScreenIntPoint(20, 20));
+  EXPECT_FALSE(resampler.InTouchingState());
+
+  CheckOutgoingEvents({
+      {Nothing(),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(10.0),
+       ScreenIntPoint(20, 20)},
+
+      {Some(idEnd2),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(20.0),
+       ScreenIntPoint(20, 20)},
+  });
+
+  // No more events should be produced from here on out.
+  resampler.NotifyFrame(Time(22.0));
+  auto outgoing = resampler.ConsumeOutgoingEvents();
+  EXPECT_TRUE(outgoing.empty());
+}
+
+TEST_F(TouchResamplerTest, InterpolationFromHistoricalData) {
+  // Interpolate from the historical data in a touch move event.
+  //
+  // Execute the following sequence:
+  //
+  // 0----------10-------16-----20-----------30--32------------
+  // * touchstart at (10, 10)
+  //             * [hist] at (20, 25) for
+  //             `---------------* touchmove at (30, 30)
+  //                      * frame
+  //                                          * touchend at (30, 30)
+  //                                              * frame
+  //
+  // And expect the following output:
+  //
+  // 0----------10-------16-----20-----------30--32------------
+  // * touchstart at (10, 10)
+  //             * [hist] at (20, 25) for
+  //             `--------* touchmove at (26, 28)
+  //                             * touchmove at (30, 30)
+  //                                          * touchend at (30, 30)
+  //
+  // The first frame should emit an interpolated touchmove from the position
+  // data in the touchmove event, and integrate the historical data point into
+  // the resampled event.
+  // The touchend should force a synthesized touchmove that returns back to a
+  // non-resampled position.
+
+  // This also tests that interpolation works for both x and y, by giving the
+  // historical datapoint different values for x and y.
+  // (26, 28) is 60% of the way from (20, 25) to (30, 30).
+
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(10, 10));
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(10.0), ScreenIntPoint(20, 25)}},
+                              Time(20.0), ScreenIntPoint(30, 30));
+  resampler.NotifyFrame(Time(16.0));
+  auto idEnd2 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(30.0),
+                             ScreenIntPoint(30, 30));
+  resampler.NotifyFrame(Time(32.0));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(10, 10)},
+
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(10.0), ScreenIntPoint(20, 25)}},
+       Time(16.0),
+       ScreenIntPoint(26, 28)},
+
+      {Nothing(),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(20.0),
+       ScreenIntPoint(30, 30)},
+
+      {Some(idEnd2),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(30.0),
+       ScreenIntPoint(30, 30)},
+  });
+}
+
+TEST_F(TouchResamplerTest, MultipleTouches) {
+  EXPECT_FALSE(resampler.InTouchingState());
+
+  // Touch start
+  MultiTouchInput inputStart0(MultiTouchInput::MULTITOUCH_START, 0, Time(0.0),
+                              0);
+  inputStart0.mTouches.AppendElement(
+      SingleTouchData(1, ScreenIntPoint(10, 10), {}, 0.0f, 0.0f));
+  auto idStart0 = resampler.ProcessEvent(std::move(inputStart0));
+  EXPECT_TRUE(resampler.InTouchingState());
+
+  // Touch move
+  MultiTouchInput inputMove1(MultiTouchInput::MULTITOUCH_MOVE, 0, Time(20.0),
+                             0);
+  inputMove1.mTouches.AppendElement(
+      SingleTouchData(1, ScreenIntPoint(30, 30), {}, 0.0f, 0.0f));
+  inputMove1.mTouches[0].mHistoricalData.AppendElement(
+      SingleTouchData::HistoricalTouchData{
+          Time(10.0), ScreenIntPoint(20, 25), {}, {}, 0.0f, 0.0f});
+  auto idMove1 = resampler.ProcessEvent(std::move(inputMove1));
+  EXPECT_TRUE(resampler.InTouchingState());
+
+  // Frame
+  resampler.NotifyFrame(Time(16.0));
+
+  // Touch move
+  MultiTouchInput inputMove2(MultiTouchInput::MULTITOUCH_MOVE, 0, Time(30.0),
+                             0);
+  inputMove2.mTouches.AppendElement(
+      SingleTouchData(1, ScreenIntPoint(30, 40), {}, 0.0f, 0.0f));
+  auto idMove2 = resampler.ProcessEvent(std::move(inputMove2));
+  EXPECT_TRUE(resampler.InTouchingState());
+
+  // Touch start
+  MultiTouchInput inputStart3(MultiTouchInput::MULTITOUCH_START, 0, Time(30.0),
+                              0);
+  inputStart3.mTouches.AppendElement(
+      SingleTouchData(2, ScreenIntPoint(100, 10), {}, 0.0f, 0.0f));
+  inputStart3.mTouches.AppendElement(
+      SingleTouchData(1, ScreenIntPoint(30, 40), {}, 0.0f, 0.0f));
+  auto idStart3 = resampler.ProcessEvent(std::move(inputStart3));
+  EXPECT_TRUE(resampler.InTouchingState());
+
+  // Touch move
+  MultiTouchInput inputMove4(MultiTouchInput::MULTITOUCH_MOVE, 0, Time(40.0),
+                             0);
+  inputMove4.mTouches.AppendElement(
+      SingleTouchData(1, ScreenIntPoint(30, 50), {}, 0.0f, 0.0f));
+  inputMove4.mTouches.AppendElement(
+      SingleTouchData(2, ScreenIntPoint(100, 30), {}, 0.0f, 0.0f));
+  auto idMove4 = resampler.ProcessEvent(std::move(inputMove4));
+  EXPECT_TRUE(resampler.InTouchingState());
+
+  // Frame
+  resampler.NotifyFrame(Time(32.0));
+
+  // Touch move
+  MultiTouchInput inputMove5(MultiTouchInput::MULTITOUCH_MOVE, 0, Time(50.0),
+                             0);
+  inputMove5.mTouches.AppendElement(
+      SingleTouchData(1, ScreenIntPoint(30, 60), {}, 0.0f, 0.0f));
+  inputMove5.mTouches.AppendElement(
+      SingleTouchData(2, ScreenIntPoint(100, 40), {}, 0.0f, 0.0f));
+  auto idMove5 = resampler.ProcessEvent(std::move(inputMove5));
+  EXPECT_TRUE(resampler.InTouchingState());
+
+  // Touch end
+  MultiTouchInput inputEnd6(MultiTouchInput::MULTITOUCH_END, 0, Time(50.0), 0);
+  // Touch point with identifier 1 is lifted
+  inputEnd6.mTouches.AppendElement(
+      SingleTouchData(1, ScreenIntPoint(30, 60), {}, 0.0f, 0.0f));
+  auto idEnd6 = resampler.ProcessEvent(std::move(inputEnd6));
+  EXPECT_TRUE(resampler.InTouchingState());
+
+  // Frame
+  resampler.NotifyFrame(Time(48.0));
+
+  // Touch move
+  MultiTouchInput inputMove7(MultiTouchInput::MULTITOUCH_MOVE, 0, Time(60.0),
+                             0);
+  inputMove7.mTouches.AppendElement(
+      SingleTouchData(2, ScreenIntPoint(100, 60), {}, 0.0f, 0.0f));
+  auto idMove7 = resampler.ProcessEvent(std::move(inputMove7));
+  EXPECT_TRUE(resampler.InTouchingState());
+
+  // Frame
+  resampler.NotifyFrame(Time(64.0));
+
+  // Touch end
+  MultiTouchInput inputEnd8(MultiTouchInput::MULTITOUCH_END, 0, Time(70.0), 0);
+  // Touch point with identifier 2 is lifted
+  inputEnd8.mTouches.AppendElement(
+      SingleTouchData(2, ScreenIntPoint(100, 60), {}, 0.0f, 0.0f));
+  auto idEnd8 = resampler.ProcessEvent(std::move(inputEnd8));
+  EXPECT_FALSE(resampler.InTouchingState());
+
+  // Check outgoing events
+  auto outgoing = resampler.ConsumeOutgoingEvents();
+  EXPECT_EQ(outgoing.size(), size_t(9));
+
+  auto outgoingStart0 = std::move(outgoing.front());
+  outgoing.pop();
+  EXPECT_EQ(outgoingStart0.mEventId, Some(idStart0));
+  CheckEvent(outgoingStart0.mEvent, MultiTouchInput::MULTITOUCH_START, {},
+             Time(0.0), ScreenIntPoint(10, 10));
+
+  auto outgoingMove1 = std::move(outgoing.front());
+  outgoing.pop();
+  EXPECT_EQ(outgoingMove1.mEventId, Some(idMove1));
+  // (26, 28) is 60% of the way from (20, 25) to (30, 30).
+  CheckEvent(outgoingMove1.mEvent, MultiTouchInput::MULTITOUCH_MOVE,
+             {{Time(10.0), ScreenIntPoint(20, 25)}}, Time(16.0),
+             ScreenIntPoint(26, 28));
+
+  auto outgoingMove2 = std::move(outgoing.front());
+  outgoing.pop();
+  EXPECT_EQ(outgoingMove2.mEventId, Some(idMove2));
+  CheckEvent(outgoingMove2.mEvent, MultiTouchInput::MULTITOUCH_MOVE,
+             {{Time(20.0), ScreenIntPoint(30, 30)}}, Time(30.0),
+             ScreenIntPoint(30, 40));
+
+  auto outgoingStart3 = std::move(outgoing.front());
+  outgoing.pop();
+  EXPECT_EQ(outgoingStart3.mEventId, Some(idStart3));
+  EXPECT_EQ(outgoingStart3.mEvent.mType, MultiTouchInput::MULTITOUCH_START);
+  CheckTime(outgoingStart3.mEvent.mTimeStamp, Time(30.0));
+  EXPECT_EQ(outgoingStart3.mEvent.mTouches.Length(), size_t(2));
+  // touch order should be taken from the original touch start event
+  EXPECT_EQ(outgoingStart3.mEvent.mTouches[0].mIdentifier, 2);
+  EXPECT_EQ(outgoingStart3.mEvent.mTouches[0].mScreenPoint,
+            ScreenIntPoint(100, 10));
+  EXPECT_EQ(outgoingStart3.mEvent.mTouches[1].mIdentifier, 1);
+  EXPECT_EQ(outgoingStart3.mEvent.mTouches[1].mScreenPoint,
+            ScreenIntPoint(30, 40));
+
+  auto outgoingMove4 = std::move(outgoing.front());
+  outgoing.pop();
+  EXPECT_EQ(outgoingMove4.mEventId, Some(idMove4));
+  EXPECT_EQ(outgoingMove4.mEvent.mType, MultiTouchInput::MULTITOUCH_MOVE);
+  CheckTime(outgoingMove4.mEvent.mTimeStamp, Time(32.0));
+  EXPECT_EQ(outgoingMove4.mEvent.mTouches.Length(), size_t(2));
+  // Touch order should be taken from the original touch move event.
+  // Both touches should be resampled.
+  EXPECT_EQ(outgoingMove4.mEvent.mTouches[0].mIdentifier, 1);
+  EXPECT_EQ(outgoingMove4.mEvent.mTouches[0].mScreenPoint,
+            ScreenIntPoint(30, 42));
+  EXPECT_EQ(outgoingMove4.mEvent.mTouches[1].mIdentifier, 2);
+  EXPECT_EQ(outgoingMove4.mEvent.mTouches[1].mScreenPoint,
+            ScreenIntPoint(100, 14));
+
+  auto outgoingMove5 = std::move(outgoing.front());
+  outgoing.pop();
+  EXPECT_EQ(outgoingMove5.mEventId, Some(idMove5));
+  EXPECT_EQ(outgoingMove5.mEvent.mType, MultiTouchInput::MULTITOUCH_MOVE);
+  CheckTime(outgoingMove5.mEvent.mTimeStamp, Time(50.0));
+  EXPECT_EQ(outgoingMove5.mEvent.mTouches.Length(), size_t(2));
+  // touch order should be taken from the original touch move event
+  EXPECT_EQ(outgoingMove5.mEvent.mTouches[0].mIdentifier, 1);
+  EXPECT_EQ(outgoingMove5.mEvent.mTouches[0].mScreenPoint,
+            ScreenIntPoint(30, 60));
+  EXPECT_EQ(outgoingMove5.mEvent.mTouches[0].mHistoricalData.Length(),
+            size_t(1));
+  CheckTime(outgoingMove5.mEvent.mTouches[0].mHistoricalData[0].mTimeStamp,
+            Time(40.0));
+  EXPECT_EQ(outgoingMove5.mEvent.mTouches[0].mHistoricalData[0].mScreenPoint,
+            ScreenIntPoint(30, 50));
+  EXPECT_EQ(outgoingMove5.mEvent.mTouches[1].mIdentifier, 2);
+  EXPECT_EQ(outgoingMove5.mEvent.mTouches[1].mScreenPoint,
+            ScreenIntPoint(100, 40));
+  EXPECT_EQ(outgoingMove5.mEvent.mTouches[1].mHistoricalData.Length(),
+            size_t(1));
+  CheckTime(outgoingMove5.mEvent.mTouches[1].mHistoricalData[0].mTimeStamp,
+            Time(40.0));
+  EXPECT_EQ(outgoingMove5.mEvent.mTouches[1].mHistoricalData[0].mScreenPoint,
+            ScreenIntPoint(100, 30));
+
+  auto outgoingEnd6 = std::move(outgoing.front());
+  outgoing.pop();
+  EXPECT_EQ(outgoingEnd6.mEventId, Some(idEnd6));
+  CheckEvent(outgoingEnd6.mEvent, MultiTouchInput::MULTITOUCH_END, {},
+             Time(50.0), ScreenIntPoint(30, 60));
+
+  auto outgoingMove7 = std::move(outgoing.front());
+  outgoing.pop();
+  EXPECT_EQ(outgoingMove7.mEventId, Some(idMove7));
+  // No extrapolation because the frame at 64.0 cleared the data points because
+  // there was no pending touch move event at that point
+  CheckEvent(outgoingMove7.mEvent, MultiTouchInput::MULTITOUCH_MOVE, {},
+             Time(60.0), ScreenIntPoint(100, 60));
+  EXPECT_EQ(outgoingMove7.mEvent.mTouches[0].mIdentifier, 2);
+
+  auto outgoingEnd8 = std::move(outgoing.front());
+  outgoing.pop();
+  EXPECT_EQ(outgoingEnd8.mEventId, Some(idEnd8));
+  CheckEvent(outgoingEnd8.mEvent, MultiTouchInput::MULTITOUCH_END, {},
+             Time(70.0), ScreenIntPoint(100, 60));
+}
+
+TEST_F(TouchResamplerTest, MovingPauses) {
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(10, 10));
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(10.0),
+                              ScreenIntPoint(20, 20));
+  resampler.NotifyFrame(Time(16.0));
+  auto idMove2 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(30.0),
+                              ScreenIntPoint(40, 40));
+  resampler.NotifyFrame(Time(32.0));
+  auto idMove3 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(40.0),
+                              ScreenIntPoint(50, 40));
+  resampler.NotifyFrame(Time(48.0));
+  resampler.NotifyFrame(Time(64.0));
+  auto idEnd4 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(70.0),
+                             ScreenIntPoint(50, 40));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(10, 10)},
+
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(10.0), ScreenIntPoint(20, 20)}},
+       Time(16.0),
+       ScreenIntPoint(26, 26)},
+
+      {Some(idMove2),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(30.0), ScreenIntPoint(40, 40)}},
+       Time(32.0),
+       ScreenIntPoint(42, 42)},
+
+      {Some(idMove3),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(40.0), ScreenIntPoint(50, 40)}},
+       Time(48.0),
+       ScreenIntPoint(58, 40)},
+
+      // There was no event between two frames here, so we expect a reset event,
+      // so that we pause at a non-resampled position.
+      {Nothing(),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(48.0),
+       ScreenIntPoint(50, 40)},
+
+      {Some(idEnd4),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(70.0),
+       ScreenIntPoint(50, 40)},
+  });
+}
+
+TEST_F(TouchResamplerTest, MixedInterAndExtrapolation) {
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(0, 0));
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(10.0),
+                              ScreenIntPoint(0, 10));
+  resampler.NotifyFrame(Time(11.0));  // 16 - 5
+  auto idMove2 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(20.0), ScreenIntPoint(0, 20)}}, Time(30.0),
+                              ScreenIntPoint(0, 30));
+  resampler.NotifyFrame(Time(27.0));  // 32 - 5
+  auto idMove3 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(40.0),
+                              ScreenIntPoint(0, 40));
+  resampler.NotifyFrame(Time(43.0));  // 48 - 5
+  auto idMove4 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(50.0), ScreenIntPoint(0, 50)}}, Time(60.0),
+                              ScreenIntPoint(0, 60));
+  resampler.NotifyFrame(Time(59.0));  // 64 - 5
+  auto idEnd5 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(70.0),
+                             ScreenIntPoint(0, 60));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(0, 0)},
+
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(10.0), ScreenIntPoint(0, 10)}},
+       Time(11.0),
+       ScreenIntPoint(0, 11)},
+
+      {Some(idMove2),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(20.0), ScreenIntPoint(0, 20)}},
+       Time(27.0),
+       ScreenIntPoint(0, 27)},
+
+      {Some(idMove3),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(30.0), ScreenIntPoint(0, 30)},
+        {Time(40.0), ScreenIntPoint(0, 40)}},
+       Time(43.0),
+       ScreenIntPoint(0, 43)},
+
+      {Some(idMove4),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(50.0), ScreenIntPoint(0, 50)}},
+       Time(59.0),
+       ScreenIntPoint(0, 59)},
+
+      {Nothing(),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(60.0),
+       ScreenIntPoint(0, 60)},
+
+      {Some(idEnd5),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(70.0),
+       ScreenIntPoint(0, 60)},
+  });
+}
+
+TEST_F(TouchResamplerTest, MultipleMoveEvents) {
+  // Test what happens if multiple touch move events appear between two frames.
+  // This scenario shouldn't occur on Android but we should be able to deal with
+  // it anyway. Check that we don't discard any event IDs.
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(0, 0));
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(10.0),
+                              ScreenIntPoint(0, 10));
+  resampler.NotifyFrame(Time(11.0));  // 16 - 5
+  auto idMove2 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(20.0), ScreenIntPoint(0, 20)}}, Time(30.0),
+                              ScreenIntPoint(0, 30));
+  auto idMove3 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(40.0),
+                              ScreenIntPoint(0, 40));
+  auto idMove4 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(45.0), ScreenIntPoint(0, 45)}}, Time(50.0),
+                              ScreenIntPoint(0, 50));
+  auto idMove5 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE, {}, Time(55.0),
+                              ScreenIntPoint(0, 55));
+  resampler.NotifyFrame(Time(43.0));  // 48 - 5
+  resampler.NotifyFrame(Time(59.0));  // 64 - 5
+  auto idEnd5 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(70.0),
+                             ScreenIntPoint(0, 60));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(0, 0)},
+
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(10.0), ScreenIntPoint(0, 10)}},
+       Time(11.0),
+       ScreenIntPoint(0, 11)},
+
+      {Some(idMove2),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(20.0), ScreenIntPoint(0, 20)}},
+       Time(30.0),
+       ScreenIntPoint(0, 30)},
+
+      {Some(idMove3),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(40.0),
+       ScreenIntPoint(0, 40)},
+
+      {Some(idMove4),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(43.0),
+       ScreenIntPoint(0, 43)},
+
+      {Some(idMove5),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(45.0), ScreenIntPoint(0, 45)},
+        {Time(50.0), ScreenIntPoint(0, 50)},
+        {Time(55.0), ScreenIntPoint(0, 55)}},
+       Time(59.0),
+       ScreenIntPoint(0, 59)},
+
+      {Nothing(),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(59.0),
+       ScreenIntPoint(0, 55)},
+
+      {Some(idEnd5),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(70.0),
+       ScreenIntPoint(0, 60)},
+  });
+}
+
+TEST_F(TouchResamplerTest, LimitFuturePrediction) {
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(0, 0));
+  // Fingers move until time 44, then pause. UI thread is occupied until 64.
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(20.0), ScreenIntPoint(0, 20)},
+                               {Time(32.0), ScreenIntPoint(0, 32)}},
+                              Time(44.0), ScreenIntPoint(0, 44));
+  resampler.NotifyFrame(Time(59.0));  // 64 - 5
+  auto idEnd2 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(70.0),
+                             ScreenIntPoint(0, 44));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(0, 0)},
+
+      // kTouchResampleMaxPredictMs == 8
+      // Refuse to predict more than 8ms into the future, the fingers might have
+      // paused. Make an event for time 52 (= 44 + 8) instead of 59.
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(20.0), ScreenIntPoint(0, 20)},
+        {Time(32.0), ScreenIntPoint(0, 32)},
+        {Time(44.0), ScreenIntPoint(0, 44)}},
+       Time(52.0),
+       ScreenIntPoint(0, 52)},
+
+      {Nothing(),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(52.0),
+       ScreenIntPoint(0, 44)},
+
+      {Some(idEnd2),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(70.0),
+       ScreenIntPoint(0, 44)},
+  });
+}
+
+TEST_F(TouchResamplerTest, LimitBacksampling) {
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(0, 0));
+  // Fingers move until time 44, then pause. UI thread is occupied until 64.
+  // Then we get a frame callback with a very outdated frametime.
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(20.0), ScreenIntPoint(0, 20)},
+                               {Time(32.0), ScreenIntPoint(0, 32)}},
+                              Time(44.0), ScreenIntPoint(0, 44));
+  resampler.NotifyFrame(Time(11.0));  // 16 - 5
+  auto idEnd2 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(70.0),
+                             ScreenIntPoint(0, 44));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(0, 0)},
+
+      // kTouchResampleMaxBacksampleMs == 20
+      // Refuse to sample further back than 20ms before the last data point.
+      // Make an event for time 24 (= 44 - 20) instead of time 11.
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(20.0), ScreenIntPoint(0, 20)}},
+       Time(24.0),
+       ScreenIntPoint(0, 24)},
+
+      {Nothing(),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(32.0), ScreenIntPoint(0, 32)}},
+       Time(44.0),
+       ScreenIntPoint(0, 44)},
+
+      {Some(idEnd2),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(70.0),
+       ScreenIntPoint(0, 44)},
+  });
+}
+
+TEST_F(TouchResamplerTest, DontExtrapolateFromOldTouch) {
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(0, 0));
+  // Fingers move until time 40, then pause. UI thread is occupied until 64.
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(20.0), ScreenIntPoint(0, 20)},
+                               {Time(30.0), ScreenIntPoint(0, 30)}},
+                              Time(40.0), ScreenIntPoint(0, 40));
+  resampler.NotifyFrame(Time(59.0));  // 64 - 5
+  auto idEnd2 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(70.0),
+                             ScreenIntPoint(0, 44));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(0, 0)},
+
+      // kTouchResampleOldTouchThresholdMs == 17
+      // Refuse to extrapolate from a data point that's more than 17ms older
+      // than the frame time.
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(20.0), ScreenIntPoint(0, 20)},
+        {Time(30.0), ScreenIntPoint(0, 30)}},
+       Time(40.0),
+       ScreenIntPoint(0, 40)},
+
+      {Some(idEnd2),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(70.0),
+       ScreenIntPoint(0, 44)},
+  });
+}
+
+TEST_F(TouchResamplerTest, DontExtrapolateIfTooOld) {
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(0, 0));
+  // Fingers move until time 10, pause, and move again at 55.
+  // UI thread is occupied until 64.
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(10.0), ScreenIntPoint(0, 10)}}, Time(55.0),
+                              ScreenIntPoint(0, 55));
+  resampler.NotifyFrame(Time(59.0));  // 64 - 5
+  auto idEnd2 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(70.0),
+                             ScreenIntPoint(0, 60));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(0, 0)},
+
+      // kTouchResampleWindowSize == 40
+      // Refuse to resample between two data points that are more than 40ms
+      // apart.
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(10.0), ScreenIntPoint(0, 10)}},
+       Time(55.0),
+       ScreenIntPoint(0, 55)},
+
+      {Some(idEnd2),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(70.0),
+       ScreenIntPoint(0, 60)},
+  });
+}
+
+TEST_F(TouchResamplerTest, DontInterpolateIfTooOld) {
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(0, 0));
+  // Fingers move until time 10, pause, and move again at 60.
+  // UI thread is occupied until 64.
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(10.0), ScreenIntPoint(0, 10)}}, Time(60.0),
+                              ScreenIntPoint(0, 60));
+  resampler.NotifyFrame(Time(59.0));  // 64 - 5
+  auto idEnd2 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(70.0),
+                             ScreenIntPoint(0, 60));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(0, 0)},
+
+      // kTouchResampleWindowSize == 40
+      // Refuse to resample between two data points that are more than 40ms
+      // apart.
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(10.0), ScreenIntPoint(0, 10)}},
+       Time(60.0),
+       ScreenIntPoint(0, 60)},
+
+      {Some(idEnd2),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(70.0),
+       ScreenIntPoint(0, 60)},
+  });
+}
+
+TEST_F(TouchResamplerTest, DiscardOutdatedHistoricalData) {
+  auto idStart0 = ProcessEvent(MultiTouchInput::MULTITOUCH_START, {}, Time(0.0),
+                               ScreenIntPoint(0, 0));
+  auto idMove1 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(10.0), ScreenIntPoint(0, 10)}}, Time(16.0),
+                              ScreenIntPoint(0, 16));
+  resampler.NotifyFrame(Time(20.0));
+  auto idMove2 = ProcessEvent(MultiTouchInput::MULTITOUCH_MOVE,
+                              {{Time(18.0), ScreenIntPoint(0, 18)}}, Time(25.0),
+                              ScreenIntPoint(0, 25));
+  auto idEnd3 = ProcessEvent(MultiTouchInput::MULTITOUCH_END, {}, Time(35.0),
+                             ScreenIntPoint(0, 25));
+
+  CheckOutgoingEvents({
+      {Some(idStart0),
+       MultiTouchInput::MULTITOUCH_START,
+       {},
+       Time(0.0),
+       ScreenIntPoint(0, 0)},
+
+      {Some(idMove1),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {{Time(10.0), ScreenIntPoint(0, 10)},
+        {Time(16.0), ScreenIntPoint(0, 16)}},
+       Time(20.0),
+       ScreenIntPoint(0, 20)},
+
+      // Discard the historical data point from time 18, because we've already
+      // sent out an event with time 20 and don't want to go back before that.
+      {Some(idMove2),
+       MultiTouchInput::MULTITOUCH_MOVE,
+       {},
+       Time(25.0),
+       ScreenIntPoint(0, 25)},
+
+      {Some(idEnd3),
+       MultiTouchInput::MULTITOUCH_END,
+       {},
+       Time(35.0),
+       ScreenIntPoint(0, 25)},
+  });
+}
diff --git a/widget/tests/gtest/TestWinHeaderOnlyUtils.cpp b/widget/tests/gtest/TestWinHeaderOnlyUtils.cpp
new file mode 100644
index 0000000000..5ac361fea0
--- /dev/null
+++ b/widget/tests/gtest/TestWinHeaderOnlyUtils.cpp
@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+
+#include <shlwapi.h>
+
+TEST(WinHeaderOnlyUtils, MozPathGetDriveNumber)
+{
+  constexpr auto TestPathGetDriveNumber = [](const wchar_t* aPath) {
+    return mozilla::MozPathGetDriveNumber(aPath) ==
+           ::PathGetDriveNumberW(aPath);
+  };
+  EXPECT_TRUE(TestPathGetDriveNumber(nullptr));
+  EXPECT_TRUE(TestPathGetDriveNumber(L""));
+  EXPECT_TRUE(TestPathGetDriveNumber(L" :"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"a:"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"C:\\file"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"x:/file"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"@:\\\\"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"B"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"abc:\\file"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\:A"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\\\"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\\\\\"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\\\?"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\\\?\\"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\\\?\\\\"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\\\?\\c:\\"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\\\?\\A"));
+  EXPECT_TRUE(TestPathGetDriveNumber(L"\\\\?\\ \\"));
+}
diff --git a/widget/tests/gtest/TestWinMessageLoggingUtils.cpp b/widget/tests/gtest/TestWinMessageLoggingUtils.cpp
new file mode 100644
index 0000000000..b0ab09f866
--- /dev/null
+++ b/widget/tests/gtest/TestWinMessageLoggingUtils.cpp
@@ -0,0 +1,101 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

+/* vim: set ts=8 sts=2 et sw=2 tw=80: */

+/* This Source Code Form is subject to the terms of the Mozilla Public

+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,

+ * You can obtain one at http://mozilla.org/MPL/2.0/. */

+

+#include "gtest/gtest.h"

+#include "windows/nsWindowDbg.h"

+

+using namespace mozilla;

+using namespace mozilla::widget;

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_CombinationFlagsHandledFirst)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x3, "COMBO"}, {0x1, "ONE"}, {0x2, "TWO"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x3, flags, nullptr));

+  EXPECT_STREQ("COMBO", result.get());

+}

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_SingleFlag)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x1, "ONE"}, {0x2, "TWO"}, {0x4, "FOUR"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x4, flags, nullptr));

+  EXPECT_STREQ("FOUR", result.get());

+}

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_SingleFlagWithName)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x1, "ONE"}, {0x2, "TWO"}, {0x4, "FOUR"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x4, flags, "paramName"));

+  EXPECT_STREQ("paramName=FOUR", result.get());

+}

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_MultipleFlags)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x1, "ONE"}, {0x2, "TWO"}, {0x4, "FOUR"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x5, flags, nullptr));

+  EXPECT_STREQ("ONE|FOUR", result.get());

+}

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_NoFlags)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x1, "ONE"}, {0x2, "TWO"}, {0x4, "FOUR"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x8, flags, nullptr));

+  EXPECT_STREQ("Unknown (0x00000008)", result.get());

+}

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_OnlySomeFlagsMatch)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x1, "ONE"}, {0x2, "TWO"}, {0x4, "FOUR"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x9, flags, nullptr));

+  EXPECT_STREQ("ONE|Unknown (0x00000008)", result.get());

+}

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_FlagsMatch_NoZeroReturned)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x1, "ONE"}, {0x2, "TWO"}, {0x4, "FOUR"}, {0x0, "ZERO"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x2, flags, nullptr));

+  EXPECT_STREQ("TWO", result.get());

+}

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_NoFlagsMatch_NoZeroReturned)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x1, "ONE"}, {0x2, "TWO"}, {0x4, "FOUR"}, {0x0, "ZERO"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x8, flags, nullptr));

+  EXPECT_STREQ("Unknown (0x00000008)", result.get());

+}

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_NameAndNoFlagsMatch_NoZeroReturned)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x1, "ONE"}, {0x2, "TWO"}, {0x4, "FOUR"}, {0x0, "ZERO"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x8, flags, "paramName"));

+  EXPECT_STREQ("paramName=Unknown (0x00000008)", result.get());

+}

+

+TEST(WinMessageLoggingUtils, AppendFlagsInfo_ValueIsZero_ZeroReturned)

+{

+  const nsTArray<EnumValueAndName> flags = {

+      {0x1, "ONE"}, {0x2, "TWO"}, {0x4, "FOUR"}, {0x0, "ZERO"}};

+  nsAutoCString result;

+  EXPECT_EQ(true, AppendFlagsInfo(result, 0x0, flags, nullptr));

+  EXPECT_STREQ("ZERO", result.get());

+}

diff --git a/widget/tests/gtest/TestWinWindowOcclusionTracker.cpp b/widget/tests/gtest/TestWinWindowOcclusionTracker.cpp
new file mode 100644
index 0000000000..b1f1114a3a
--- /dev/null
+++ b/widget/tests/gtest/TestWinWindowOcclusionTracker.cpp
@@ -0,0 +1,167 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+
+#include <dwmapi.h>
+#include <windows.h>
+
+#include "MockWinWidget.h"
+#include "mozilla/widget/WinWindowOcclusionTracker.h"
+#include "mozilla/WindowsVersion.h"
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+class WinWindowOcclusionTrackerTest : public ::testing::Test {
+ protected:
+  HWND CreateNativeWindow(DWORD aStyle, DWORD aExStyle) {
+    mMockWinWidget =
+        MockWinWidget::Create(WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN | aStyle,
+                              aExStyle, LayoutDeviceIntRect(0, 0, 100, 100));
+    EXPECT_NE(nullptr, mMockWinWidget.get());
+    HWND hwnd = mMockWinWidget->GetWnd();
+    HRGN region = ::CreateRectRgn(0, 0, 0, 0);
+    EXPECT_NE(nullptr, region);
+    if (::GetWindowRgn(hwnd, region) == COMPLEXREGION) {
+      // On Windows 7, the newly created window has a complex region, which
+      // means it will be ignored during the occlusion calculation. So, force
+      // it to have a simple region so that we get test coverage on win 7.
+      RECT boundingRect;
+      EXPECT_TRUE(::GetWindowRect(hwnd, &boundingRect));
+      HRGN rectangularRegion = ::CreateRectRgnIndirect(&boundingRect);
+      EXPECT_NE(nullptr, rectangularRegion);
+      ::SetWindowRgn(hwnd, rectangularRegion, /* bRedraw = */ TRUE);
+      ::DeleteObject(rectangularRegion);
+    }
+    ::DeleteObject(region);
+
+    ::ShowWindow(hwnd, SW_SHOWNORMAL);
+    EXPECT_TRUE(UpdateWindow(hwnd));
+    return hwnd;
+  }
+
+  // Wrapper around IsWindowVisibleAndFullyOpaque so only the test class
+  // needs to be a friend of NativeWindowOcclusionTrackerWin.
+  bool CheckWindowVisibleAndFullyOpaque(HWND aHWnd,
+                                        LayoutDeviceIntRect* aWinRect) {
+    bool ret = WinWindowOcclusionTracker::IsWindowVisibleAndFullyOpaque(
+        aHWnd, aWinRect);
+    // In general, if IsWindowVisibleAndFullyOpaque returns false, the
+    // returned rect should not be altered.
+    if (!ret) {
+      EXPECT_EQ(*aWinRect, LayoutDeviceIntRect(0, 0, 0, 0));
+    }
+    return ret;
+  }
+
+  RefPtr<MockWinWidget> mMockWinWidget;
+};
+
+TEST_F(WinWindowOcclusionTrackerTest, VisibleOpaqueWindow) {
+  HWND hwnd = CreateNativeWindow(/* aStyle = */ 0, /* aExStyle = */ 0);
+  LayoutDeviceIntRect returnedRect;
+  // Normal windows should be visible.
+  EXPECT_TRUE(CheckWindowVisibleAndFullyOpaque(hwnd, &returnedRect));
+
+  // Check that the returned rect == the actual window rect of the hwnd.
+  RECT winRect;
+  ASSERT_TRUE(::GetWindowRect(hwnd, &winRect));
+  EXPECT_EQ(returnedRect, LayoutDeviceIntRect(winRect.left, winRect.top,
+                                              winRect.right - winRect.left,
+                                              winRect.bottom - winRect.top));
+}
+
+TEST_F(WinWindowOcclusionTrackerTest, MinimizedWindow) {
+  HWND hwnd = CreateNativeWindow(/* aStyle = */ 0, /* aExStyle = */ 0);
+  LayoutDeviceIntRect winRect;
+  ::ShowWindow(hwnd, SW_MINIMIZE);
+  // Minimized windows are not considered visible.
+  EXPECT_FALSE(CheckWindowVisibleAndFullyOpaque(hwnd, &winRect));
+}
+
+TEST_F(WinWindowOcclusionTrackerTest, TransparentWindow) {
+  HWND hwnd = CreateNativeWindow(/* aStyle = */ 0, WS_EX_TRANSPARENT);
+  LayoutDeviceIntRect winRect;
+  // Transparent windows are not considered visible and opaque.
+  EXPECT_FALSE(CheckWindowVisibleAndFullyOpaque(hwnd, &winRect));
+}
+
+TEST_F(WinWindowOcclusionTrackerTest, ToolWindow) {
+  HWND hwnd = CreateNativeWindow(/* aStyle = */ 0, WS_EX_TOOLWINDOW);
+  LayoutDeviceIntRect winRect;
+  // Tool windows are not considered visible and opaque.
+  EXPECT_FALSE(CheckWindowVisibleAndFullyOpaque(hwnd, &winRect));
+}
+
+TEST_F(WinWindowOcclusionTrackerTest, LayeredAlphaWindow) {
+  HWND hwnd = CreateNativeWindow(/* aStyle = */ 0, WS_EX_LAYERED);
+  LayoutDeviceIntRect winRect;
+  BYTE alpha = 1;
+  DWORD flags = LWA_ALPHA;
+  COLORREF colorRef = RGB(1, 1, 1);
+  SetLayeredWindowAttributes(hwnd, colorRef, alpha, flags);
+  // Layered windows with alpha < 255 are not considered visible and opaque.
+  EXPECT_FALSE(CheckWindowVisibleAndFullyOpaque(hwnd, &winRect));
+}
+
+TEST_F(WinWindowOcclusionTrackerTest, UpdatedLayeredAlphaWindow) {
+  HWND hwnd = CreateNativeWindow(/* aStyle = */ 0, WS_EX_LAYERED);
+  LayoutDeviceIntRect winRect;
+  HDC hdc = ::CreateCompatibleDC(nullptr);
+  EXPECT_NE(nullptr, hdc);
+  BLENDFUNCTION blend = {AC_SRC_OVER, 0x00, 0xFF, AC_SRC_ALPHA};
+
+  ::UpdateLayeredWindow(hwnd, hdc, nullptr, nullptr, nullptr, nullptr,
+                        RGB(0xFF, 0xFF, 0xFF), &blend, ULW_OPAQUE);
+  // Layered windows set up with UpdateLayeredWindow instead of
+  // SetLayeredWindowAttributes should not be considered visible and opaque.
+  EXPECT_FALSE(CheckWindowVisibleAndFullyOpaque(hwnd, &winRect));
+  ::DeleteDC(hdc);
+}
+
+TEST_F(WinWindowOcclusionTrackerTest, LayeredNonAlphaWindow) {
+  HWND hwnd = CreateNativeWindow(/* aStyle = */ 0, WS_EX_LAYERED);
+  LayoutDeviceIntRect winRect;
+  BYTE alpha = 1;
+  DWORD flags = 0;
+  COLORREF colorRef = RGB(1, 1, 1);
+  ::SetLayeredWindowAttributes(hwnd, colorRef, alpha, flags);
+  // Layered non alpha windows are considered visible and opaque.
+  EXPECT_TRUE(CheckWindowVisibleAndFullyOpaque(hwnd, &winRect));
+}
+
+TEST_F(WinWindowOcclusionTrackerTest, ComplexRegionWindow) {
+  HWND hwnd = CreateNativeWindow(/* aStyle = */ 0, /* aExStyle = */ 0);
+  LayoutDeviceIntRect winRect;
+  // Create a region with rounded corners, which should be a complex region.
+  HRGN region = CreateRoundRectRgn(1, 1, 100, 100, 5, 5);
+  EXPECT_NE(nullptr, region);
+  ::SetWindowRgn(hwnd, region, /* bRedraw = */ TRUE);
+  // Windows with complex regions are not considered visible and fully opaque.
+  EXPECT_FALSE(CheckWindowVisibleAndFullyOpaque(hwnd, &winRect));
+  DeleteObject(region);
+}
+
+TEST_F(WinWindowOcclusionTrackerTest, PopupWindow) {
+  HWND hwnd = CreateNativeWindow(WS_POPUP, /* aExStyle = */ 0);
+  LayoutDeviceIntRect winRect;
+  // Normal Popup Windows are not considered visible.
+  EXPECT_FALSE(CheckWindowVisibleAndFullyOpaque(hwnd, &winRect));
+}
+
+TEST_F(WinWindowOcclusionTrackerTest, CloakedWindow) {
+  // Cloaking is only supported in Windows 8 and above.
+  if (!IsWin8OrLater()) {
+    return;
+  }
+  HWND hwnd = CreateNativeWindow(/* aStyle = */ 0, /* aExStyle = */ 0);
+  LayoutDeviceIntRect winRect;
+  BOOL cloak = TRUE;
+  ::DwmSetWindowAttribute(hwnd, DWMWA_CLOAK, &cloak, sizeof(cloak));
+  // Cloaked Windows are not considered visible.
+  EXPECT_FALSE(CheckWindowVisibleAndFullyOpaque(hwnd, &winRect));
+}
diff --git a/widget/tests/gtest/TestWinWindowOcclusionTrackerInteractive.cpp b/widget/tests/gtest/TestWinWindowOcclusionTrackerInteractive.cpp
new file mode 100644
index 0000000000..13cd95651c
--- /dev/null
+++ b/widget/tests/gtest/TestWinWindowOcclusionTrackerInteractive.cpp
@@ -0,0 +1,402 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+
+#include "MockWinWidget.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/widget/WinEventObserver.h"
+#include "mozilla/widget/WinWindowOcclusionTracker.h"
+#include "nsThreadUtils.h"
+#include "Units.h"
+#include "WinUtils.h"
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+#define PREF_DISPLAY_STATE \
+  "widget.windows.window_occlusion_tracking_display_state.enabled"
+#define PREF_SESSION_LOCK \
+  "widget.windows.window_occlusion_tracking_session_lock.enabled"
+
+class WinWindowOcclusionTrackerInteractiveTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    // Shut down WinWindowOcclusionTracker if it exists.
+    // This could happen when WinWindowOcclusionTracker was initialized by other
+    // gtest
+    if (WinWindowOcclusionTracker::Get()) {
+      WinWindowOcclusionTracker::ShutDown();
+    }
+    EXPECT_EQ(nullptr, WinWindowOcclusionTracker::Get());
+
+    WinWindowOcclusionTracker::Ensure();
+    EXPECT_NE(nullptr, WinWindowOcclusionTracker::Get());
+
+    WinWindowOcclusionTracker::Get()->EnsureDisplayStatusObserver();
+    WinWindowOcclusionTracker::Get()->EnsureSessionChangeObserver();
+  }
+
+  void TearDown() override {
+    WinWindowOcclusionTracker::ShutDown();
+    EXPECT_EQ(nullptr, WinWindowOcclusionTracker::Get());
+  }
+
+  void SetNativeWindowBounds(HWND aHWnd, const LayoutDeviceIntRect aBounds) {
+    RECT wr;
+    wr.left = aBounds.X();
+    wr.top = aBounds.Y();
+    wr.right = aBounds.XMost();
+    wr.bottom = aBounds.YMost();
+
+    ::AdjustWindowRectEx(&wr, ::GetWindowLong(aHWnd, GWL_STYLE), FALSE,
+                         ::GetWindowLong(aHWnd, GWL_EXSTYLE));
+
+    // Make sure to keep the window onscreen, as AdjustWindowRectEx() may have
+    // moved part of it offscreen. But, if the original requested bounds are
+    // offscreen, don't adjust the position.
+    LayoutDeviceIntRect windowBounds(wr.left, wr.top, wr.right - wr.left,
+                                     wr.bottom - wr.top);
+
+    if (aBounds.X() >= 0) {
+      windowBounds.x = std::max(0, windowBounds.X());
+    }
+    if (aBounds.Y() >= 0) {
+      windowBounds.y = std::max(0, windowBounds.Y());
+    }
+    ::SetWindowPos(aHWnd, HWND_TOP, windowBounds.X(), windowBounds.Y(),
+                   windowBounds.Width(), windowBounds.Height(),
+                   SWP_NOREPOSITION);
+    EXPECT_TRUE(::UpdateWindow(aHWnd));
+  }
+
+  void CreateNativeWindowWithBounds(LayoutDeviceIntRect aBounds) {
+    mMockWinWidget = MockWinWidget::Create(
+        WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN, /* aExStyle = */ 0, aBounds);
+    EXPECT_NE(nullptr, mMockWinWidget.get());
+    HWND hwnd = mMockWinWidget->GetWnd();
+    SetNativeWindowBounds(hwnd, aBounds);
+    HRGN region = ::CreateRectRgn(0, 0, 0, 0);
+    EXPECT_NE(nullptr, region);
+    if (::GetWindowRgn(hwnd, region) == COMPLEXREGION) {
+      // On Windows 7, the newly created window has a complex region, which
+      // means it will be ignored during the occlusion calculation. So, force
+      // it to have a simple region so that we get test coverage on win 7.
+      RECT boundingRect;
+      EXPECT_TRUE(::GetWindowRect(hwnd, &boundingRect));
+      HRGN rectangularRegion = ::CreateRectRgnIndirect(&boundingRect);
+      EXPECT_NE(nullptr, rectangularRegion);
+      ::SetWindowRgn(hwnd, rectangularRegion, /* bRedraw = */ TRUE);
+      ::DeleteObject(rectangularRegion);
+    }
+    ::DeleteObject(region);
+
+    ::ShowWindow(hwnd, SW_SHOWNORMAL);
+    EXPECT_TRUE(UpdateWindow(hwnd));
+  }
+
+  RefPtr<MockWinWidget> CreateTrackedWindowWithBounds(
+      LayoutDeviceIntRect aBounds) {
+    RefPtr<MockWinWidget> window = MockWinWidget::Create(
+        WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN, /* aExStyle */ 0, aBounds);
+    EXPECT_NE(nullptr, window.get());
+    HWND hwnd = window->GetWnd();
+    ::ShowWindow(hwnd, SW_SHOWNORMAL);
+    WinWindowOcclusionTracker::Get()->Enable(window, window->GetWnd());
+    return window;
+  }
+
+  int GetNumVisibleRootWindows() {
+    return WinWindowOcclusionTracker::Get()->mNumVisibleRootWindows;
+  }
+
+  void OnDisplayStateChanged(bool aDisplayOn) {
+    WinWindowOcclusionTracker::Get()->OnDisplayStateChanged(aDisplayOn);
+  }
+
+  RefPtr<MockWinWidget> mMockWinWidget;
+};
+
+// Simple test completely covering a tracked window with a native window.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest, SimpleOcclusion) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  window->SetExpectation(widget::OcclusionState::OCCLUDED);
+  CreateNativeWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
+
+// Simple test partially covering a tracked window with a native window.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest, PartialOcclusion) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 200, 200));
+  window->SetExpectation(widget::OcclusionState::VISIBLE);
+  CreateNativeWindowWithBounds(LayoutDeviceIntRect(0, 0, 50, 50));
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
+
+// Simple test that a partly off screen tracked window, with the on screen part
+// occluded by a native window, is considered occluded.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest, OffscreenOcclusion) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  // Move the tracked window 50 pixels offscreen to the left.
+  int screenLeft = ::GetSystemMetrics(SM_XVIRTUALSCREEN);
+  ::SetWindowPos(window->GetWnd(), HWND_TOP, screenLeft - 50, 0, 100, 100,
+                 SWP_NOZORDER | SWP_NOSIZE);
+
+  // Create a native window that covers the onscreen part of the tracked window.
+  CreateNativeWindowWithBounds(LayoutDeviceIntRect(screenLeft, 0, 50, 100));
+  window->SetExpectation(widget::OcclusionState::OCCLUDED);
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
+
+// Simple test with a tracked window and native window that do not overlap.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest, SimpleVisible) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  window->SetExpectation(widget::OcclusionState::VISIBLE);
+  CreateNativeWindowWithBounds(LayoutDeviceIntRect(200, 0, 100, 100));
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
+
+// Simple test with a minimized tracked window and native window.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest, SimpleHidden) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  CreateNativeWindowWithBounds(LayoutDeviceIntRect(200, 0, 100, 100));
+  // Iconify the tracked window and check that its occlusion state is HIDDEN.
+  ::CloseWindow(window->GetWnd());
+  window->SetExpectation(widget::OcclusionState::HIDDEN);
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
+
+// Test that minimizing and restoring a tracked window results in the occlusion
+// tracker re-registering for win events and detecting that a native window
+// occludes the tracked window.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest,
+       OcclusionAfterVisibilityToggle) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  window->SetExpectation(widget::OcclusionState::VISIBLE);
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+
+  window->SetExpectation(widget::OcclusionState::HIDDEN);
+  WinWindowOcclusionTracker::Get()->OnWindowVisibilityChanged(
+      window, /* aVisible = */ false);
+
+  // This makes the window iconic.
+  ::CloseWindow(window->GetWnd());
+
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+
+  // HIDDEN state is set synchronously by OnWindowVsiblityChanged notification,
+  // before occlusion is calculated, so the above expectation will be met w/o an
+  // occlusion calculation.
+  // Loop until an occlusion calculation has run with no non-hidden windows.
+  while (GetNumVisibleRootWindows() != 0) {
+    // Need to pump events in order for UpdateOcclusionState to get called, and
+    // update the number of non hidden windows. When that number is 0,
+    // occlusion has been calculated with no visible tracked windows.
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+
+  window->SetExpectation(widget::OcclusionState::VISIBLE);
+  WinWindowOcclusionTracker::Get()->OnWindowVisibilityChanged(
+      window, /* aVisible = */ true);
+  // This opens the window made iconic above.
+  ::OpenIcon(window->GetWnd());
+
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+
+  // Open a native window that occludes the visible tracked window.
+  window->SetExpectation(widget::OcclusionState::OCCLUDED);
+  CreateNativeWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
+
+// Test that locking the screen causes visible windows to become occluded.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest, LockScreenVisibleOcclusion) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  window->SetExpectation(widget::OcclusionState::VISIBLE);
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+
+  window->SetExpectation(widget::OcclusionState::OCCLUDED);
+  // Unfortunately, this relies on knowing that NativeWindowOcclusionTracker
+  // uses SessionChangeObserver to listen for WM_WTSSESSION_CHANGE messages, but
+  // actually locking the screen isn't feasible.
+  DWORD currentSessionId = 0;
+  ::ProcessIdToSessionId(::GetCurrentProcessId(), &currentSessionId);
+  ::PostMessage(WinEventHub::Get()->GetWnd(), WM_WTSSESSION_CHANGE,
+                WTS_SESSION_LOCK, currentSessionId);
+
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+
+    MSG msg;
+    bool gotMessage =
+        ::PeekMessageW(&msg, WinEventHub::Get()->GetWnd(), 0, 0, PM_REMOVE);
+    if (gotMessage) {
+      ::TranslateMessage(&msg);
+      ::DispatchMessageW(&msg);
+    }
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ false);
+    PR_Sleep(PR_INTERVAL_NO_WAIT);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
+
+// Test that locking the screen leaves hidden windows as hidden.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest, LockScreenHiddenOcclusion) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  // Iconify the tracked window and check that its occlusion state is HIDDEN.
+  ::CloseWindow(window->GetWnd());
+  window->SetExpectation(widget::OcclusionState::HIDDEN);
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+
+  // Force the state to VISIBLE.
+  window->NotifyOcclusionState(widget::OcclusionState::VISIBLE);
+
+  window->SetExpectation(widget::OcclusionState::HIDDEN);
+
+  // Unfortunately, this relies on knowing that NativeWindowOcclusionTracker
+  // uses SessionChangeObserver to listen for WM_WTSSESSION_CHANGE messages, but
+  // actually locking the screen isn't feasible.
+  DWORD currentSessionId = 0;
+  ::ProcessIdToSessionId(::GetCurrentProcessId(), &currentSessionId);
+  PostMessage(WinEventHub::Get()->GetWnd(), WM_WTSSESSION_CHANGE,
+              WTS_SESSION_LOCK, currentSessionId);
+
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+
+    MSG msg;
+    bool gotMessage =
+        ::PeekMessageW(&msg, WinEventHub::Get()->GetWnd(), 0, 0, PM_REMOVE);
+    if (gotMessage) {
+      ::TranslateMessage(&msg);
+      ::DispatchMessageW(&msg);
+    }
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ false);
+    PR_Sleep(PR_INTERVAL_NO_WAIT);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
+
+// Test that locking the screen from a different session doesn't mark window
+// as occluded.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest, LockScreenDifferentSession) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 200, 200));
+  window->SetExpectation(widget::OcclusionState::VISIBLE);
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+
+  // Force the state to OCCLUDED.
+  window->NotifyOcclusionState(widget::OcclusionState::OCCLUDED);
+
+  // Generate a session change lock screen with a session id that's not
+  // currentSessionId.
+  DWORD currentSessionId = 0;
+  ::ProcessIdToSessionId(::GetCurrentProcessId(), &currentSessionId);
+  ::PostMessage(WinEventHub::Get()->GetWnd(), WM_WTSSESSION_CHANGE,
+                WTS_SESSION_LOCK, currentSessionId + 1);
+
+  window->SetExpectation(widget::OcclusionState::VISIBLE);
+  // Create a native window to trigger occlusion calculation.
+  CreateNativeWindowWithBounds(LayoutDeviceIntRect(0, 0, 50, 50));
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+
+    MSG msg;
+    bool gotMessage =
+        ::PeekMessageW(&msg, WinEventHub::Get()->GetWnd(), 0, 0, PM_REMOVE);
+    if (gotMessage) {
+      ::TranslateMessage(&msg);
+      ::DispatchMessageW(&msg);
+    }
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ false);
+    PR_Sleep(PR_INTERVAL_NO_WAIT);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
+
+// Test that display off & on power state notification causes visible windows to
+// become occluded, then visible.
+TEST_F(WinWindowOcclusionTrackerInteractiveTest, DisplayOnOffHandling) {
+  RefPtr<MockWinWidget> window =
+      CreateTrackedWindowWithBounds(LayoutDeviceIntRect(0, 0, 100, 100));
+  window->SetExpectation(widget::OcclusionState::VISIBLE);
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+
+  window->SetExpectation(widget::OcclusionState::OCCLUDED);
+
+  // Turning display off and on isn't feasible, so send a notification.
+  OnDisplayStateChanged(/* aDisplayOn */ false);
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+
+  window->SetExpectation(widget::OcclusionState::VISIBLE);
+  OnDisplayStateChanged(/* aDisplayOn */ true);
+  while (window->IsExpectingCall()) {
+    WinWindowOcclusionTracker::Get()->TriggerCalculation();
+
+    NS_ProcessNextEvent(nullptr, /* aMayWait = */ true);
+  }
+  EXPECT_FALSE(window->IsExpectingCall());
+}
diff --git a/widget/tests/gtest/moz.build b/widget/tests/gtest/moz.build
new file mode 100644
index 0000000000..613844fa78
--- /dev/null
+++ b/widget/tests/gtest/moz.build
@@ -0,0 +1,27 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, you can obtain one at http://mozilla.org/MPL/2.0/.
+
+UNIFIED_SOURCES = [
+    "TestTimeConverter.cpp",
+    "TestTouchResampler.cpp",
+]
+
+if CONFIG["OS_ARCH"] == "WINNT":
+    UNIFIED_SOURCES += [
+        "MockWinWidget.cpp",
+        "TestWinHeaderOnlyUtils.cpp",
+        "TestWinMessageLoggingUtils.cpp",
+        "TestWinWindowOcclusionTracker.cpp",
+        "TestWinWindowOcclusionTrackerInteractive.cpp",
+    ]
+
+FINAL_LIBRARY = "xul-gtest"
+
+LOCAL_INCLUDES += [
+    "/widget",
+]
+
+DisableStlWrapping()