Adding upstream version 124.0.1.upstream/124.0.1

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

9 files changed, 1275 insertions, 0 deletions

diff --git a/gfx/layers/apz/public/APZInputBridge.h b/gfx/layers/apz/public/APZInputBridge.h
new file mode 100644
index 0000000000..117e4b7bb2
--- /dev/null
+++ b/gfx/layers/apz/public/APZInputBridge.h
@@ -0,0 +1,298 @@
+/* -*- 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 mozilla_layers_APZInputBridge_h
+#define mozilla_layers_APZInputBridge_h
+
+#include "Units.h"                  // for LayoutDeviceIntPoint
+#include "mozilla/EventForwards.h"  // for WidgetInputEvent, nsEventStatus
+#include "mozilla/layers/APZPublicUtils.h"       // for APZWheelAction
+#include "mozilla/layers/LayersTypes.h"          // for ScrollDirections
+#include "mozilla/layers/ScrollableLayerGuid.h"  // for ScrollableLayerGuid
+
+namespace mozilla {
+
+class InputData;
+
+namespace layers {
+
+class APZInputBridgeParent;
+class AsyncPanZoomController;
+class InputBlockState;
+class TouchBlockState;
+struct ScrollableLayerGuid;
+struct TargetConfirmationFlags;
+struct PointerEventsConsumableFlags;
+
+enum class APZHandledPlace : uint8_t {
+  Unhandled = 0,         // we know for sure that the event will not be handled
+                         // by either the root APZC or others
+  HandledByRoot = 1,     // we know for sure that the event will be handled
+                         // by the root content APZC
+  HandledByContent = 2,  // we know for sure it will be handled by a non-root
+                         // APZC or by an event listener using preventDefault()
+                         // in a document
+  Invalid = 3,
+  Last = Invalid
+};
+
+struct APZHandledResult {
+  APZHandledPlace mPlace = APZHandledPlace::Invalid;
+  SideBits mScrollableDirections = SideBits::eNone;
+  ScrollDirections mOverscrollDirections = ScrollDirections();
+
+  APZHandledResult() = default;
+  // A constructor for cases where we have the target of the input block this
+  // event is part of, the target might be adjusted to be the root in the
+  // ScrollingDownWillMoveDynamicToolbar case.
+  //
+  // NOTE: There's a case where |aTarget| is the APZC for the root content but
+  // |aPlace| has to be `HandledByContent`, for example, the root content has
+  // an event handler using preventDefault() in the callback, so call sites of
+  // this function should be responsible to set a proper |aPlace|.
+  APZHandledResult(APZHandledPlace aPlace,
+                   const AsyncPanZoomController* aTarget,
+                   bool aPopulateDirectionsForUnhandled = false);
+  APZHandledResult(APZHandledPlace aPlace, SideBits aScrollableDirections,
+                   ScrollDirections aOverscrollDirections)
+      : mPlace(aPlace),
+        mScrollableDirections(aScrollableDirections),
+        mOverscrollDirections(aOverscrollDirections) {}
+
+  bool IsHandledByContent() const {
+    return mPlace == APZHandledPlace::HandledByContent;
+  }
+  bool IsHandledByRoot() const {
+    return mPlace == APZHandledPlace::HandledByRoot;
+  }
+  bool operator==(const APZHandledResult& aOther) const {
+    return mPlace == aOther.mPlace &&
+           mScrollableDirections == aOther.mScrollableDirections &&
+           mOverscrollDirections == aOther.mOverscrollDirections;
+  }
+};
+
+/**
+ * Represents the outcome of APZ receiving and processing an input event.
+ * This is returned from APZInputBridge::ReceiveInputEvent() and related APIs.
+ */
+struct APZEventResult {
+  /**
+   * Creates a default result with a status of eIgnore, no block ID, and empty
+   * target guid.
+   */
+  APZEventResult();
+
+  /**
+   * Creates a result with a status of eIgnore, no block ID, the guid of the
+   * given initial target, and an APZHandledResult if we are sure the event
+   * is not going to be dispatched to contents.
+   */
+  APZEventResult(const RefPtr<AsyncPanZoomController>& aInitialTarget,
+                 TargetConfirmationFlags aFlags);
+
+  void SetStatusAsConsumeNoDefault() {
+    mStatus = nsEventStatus_eConsumeNoDefault;
+  }
+
+  void SetStatusAsIgnore() { mStatus = nsEventStatus_eIgnore; }
+
+  // Set mStatus to nsEventStatus_eConsumeDoDefault and set mHandledResult
+  // depending on |aTarget|.
+  void SetStatusAsConsumeDoDefault(
+      const RefPtr<AsyncPanZoomController>& aTarget);
+
+  // Set mStatus to nsEventStatus_eConsumeDoDefault, unlike above
+  // SetStatusAsConsumeDoDefault(const RefPtr<AsyncPanZoomController>&) this
+  // function doesn't mutate mHandledResult.
+  void SetStatusAsConsumeDoDefault() {
+    mStatus = nsEventStatus_eConsumeDoDefault;
+  }
+
+  // Set mStatus to nsEventStatus_eConsumeDoDefault and set mHandledResult
+  // depending on |aBlock|'s target APZC.
+  void SetStatusAsConsumeDoDefault(const InputBlockState& aBlock);
+  // Set mStatus and mHandledResult for a touch event which is not dropped
+  // altogether (i.e. the status is not eConsumeNoDefault).
+  void SetStatusForTouchEvent(const InputBlockState& aBlock,
+                              TargetConfirmationFlags aFlags,
+                              PointerEventsConsumableFlags aConsumableFlags,
+                              const AsyncPanZoomController* aTarget);
+
+  // Set mStatus and mHandledResult during in a stat of fast fling.
+  void SetStatusForFastFling(const TouchBlockState& aBlock,
+                             TargetConfirmationFlags aFlags,
+                             PointerEventsConsumableFlags aConsumableFlags,
+                             const AsyncPanZoomController* aTarget);
+
+  // DO NOT USE THIS UpdateStatus DIRECTLY. THIS FUNCTION IS ONLY FOR
+  // SERIALIZATION / DESERIALIZATION OF THIS STRUCT IN IPC.
+  void UpdateStatus(nsEventStatus aStatus) { mStatus = aStatus; }
+  nsEventStatus GetStatus() const { return mStatus; };
+
+  // DO NOT USE THIS UpdateHandledResult DIRECTLY. THIS FUNCTION IS ONLY FOR
+  // SERIALIZATION / DESERIALIZATION OF THIS STRUCT IN IPC.
+  void UpdateHandledResult(const Maybe<APZHandledResult>& aHandledResult) {
+    mHandledResult = aHandledResult;
+  }
+  const Maybe<APZHandledResult>& GetHandledResult() const {
+    return mHandledResult;
+  }
+
+  bool WillHaveDelayedResult() const {
+    return GetStatus() != nsEventStatus_eConsumeNoDefault &&
+           !GetHandledResult();
+  }
+
+ private:
+  void UpdateHandledResult(const InputBlockState& aBlock,
+                           PointerEventsConsumableFlags aConsumableFlags,
+                           const AsyncPanZoomController* aTarget,
+                           bool aDispatchToContent);
+
+  /**
+   * A status flag indicated how APZ handled the event.
+   * The interpretation of each value is as follows:
+   *
+   * nsEventStatus_eConsumeNoDefault is returned to indicate the
+   *   APZ is consuming this event and the caller should discard the event with
+   *   extreme prejudice. The exact scenarios under which this is returned is
+   *   implementation-dependent and may vary.
+   * nsEventStatus_eIgnore is returned to indicate that the APZ code didn't
+   *   use this event. This might be because it was directed at a point on
+   *   the screen where there was no APZ, or because the thing the user was
+   *   trying to do was not allowed. (For example, attempting to pan a
+   *   non-pannable document).
+   * nsEventStatus_eConsumeDoDefault is returned to indicate that the APZ
+   *   code may have used this event to do some user-visible thing. Note that
+   *   in some cases CONSUMED is returned even if the event was NOT used. This
+   *   is because we cannot always know at the time of event delivery whether
+   *   the event will be used or not. So we err on the side of sending
+   *   CONSUMED when we are uncertain.
+   */
+  nsEventStatus mStatus;
+
+  /**
+   * This is:
+   *  - set to HandledByRoot if we know for sure that the event will be handled
+   *    by the root content APZC;
+   *  - set to HandledByContent if we know for sure it will not be;
+   *  - left empty if we are unsure.
+   */
+  Maybe<APZHandledResult> mHandledResult;
+
+ public:
+  /**
+   * The guid of the APZC initially targeted by this event.
+   * This will usually be the APZC that handles the event, but in cases
+   * where the event is dispatched to content, it may end up being
+   * handled by a different APZC.
+   */
+  ScrollableLayerGuid mTargetGuid;
+  /**
+   * If this event started or was added to an input block, the id of that
+   * input block, otherwise InputBlockState::NO_BLOCK_ID.
+   */
+  uint64_t mInputBlockId;
+};
+
+/**
+ * This class lives in the main process, and is accessed via the controller
+ * thread (which is the process main thread for desktop, and the Java UI
+ * thread for Android). This class exposes a synchronous API to deliver
+ * incoming input events to APZ and modify them in-place to unapply the APZ
+ * async transform. If there is a GPU process, then this class does sync IPC
+ * calls over to the GPU process in order to accomplish this. Otherwise,
+ * APZCTreeManager overrides and implements these methods directly.
+ */
+class APZInputBridge {
+ public:
+  using InputBlockCallback = std::function<void(
+      uint64_t aInputBlockId, const APZHandledResult& aHandledResult)>;
+
+  /**
+   * General handler for incoming input events. Manipulates the frame metrics
+   * based on what type of input it is. For example, a PinchGestureEvent will
+   * cause scaling. This should only be called externally to this class, and
+   * must be called on the controller thread.
+   *
+   * This function transforms |aEvent| to have its coordinates in DOM space.
+   * This is so that the event can be passed through the DOM and content can
+   * handle them. The event may need to be converted to a WidgetInputEvent
+   * by the caller if it wants to do this.
+   *
+   * @param aEvent input event object; is modified in-place
+   * @param aCallback an optional callback to be invoked when the input block is
+   * ready for handling,
+   * @return The result of processing the event. Refer to the documentation of
+   * APZEventResult and its field.
+   */
+  virtual APZEventResult ReceiveInputEvent(
+      InputData& aEvent,
+      InputBlockCallback&& aCallback = InputBlockCallback()) = 0;
+
+  /**
+   * WidgetInputEvent handler. Transforms |aEvent| (which is assumed to be an
+   * already-existing instance of an WidgetInputEvent which may be an
+   * WidgetTouchEvent) to have its coordinates in DOM space. This is so that the
+   * event can be passed through the DOM and content can handle them.
+   *
+   * NOTE: Be careful of invoking the WidgetInputEvent variant. This can only be
+   * called on the main thread. See widget/InputData.h for more information on
+   * why we have InputData and WidgetInputEvent separated. If this function is
+   * used, the controller thread must be the main thread, or undefined behaviour
+   * may occur.
+   * NOTE: On unix, mouse events are treated as touch and are forwarded
+   * to the appropriate apz as such.
+   *
+   * See documentation for other ReceiveInputEvent above.
+   */
+  APZEventResult ReceiveInputEvent(
+      WidgetInputEvent& aEvent,
+      InputBlockCallback&& aCallback = InputBlockCallback());
+
+  // Returns the kind of wheel event action, if any, that will be (or was)
+  // performed by APZ. If this returns true, the event must not perform a
+  // synchronous scroll.
+  //
+  // Even if this returns Nothing(), all wheel events in APZ-aware widgets must
+  // be sent through APZ so they are transformed correctly for BrowserParent.
+  static Maybe<APZWheelAction> ActionForWheelEvent(WidgetWheelEvent* aEvent);
+
+ protected:
+  friend class APZInputBridgeParent;
+
+  // Methods to help process WidgetInputEvents (or manage conversion to/from
+  // InputData)
+
+  virtual void ProcessUnhandledEvent(LayoutDeviceIntPoint* aRefPoint,
+                                     ScrollableLayerGuid* aOutTargetGuid,
+                                     uint64_t* aOutFocusSequenceNumber,
+                                     LayersId* aOutLayersId) = 0;
+
+  virtual void UpdateWheelTransaction(
+      LayoutDeviceIntPoint aRefPoint, EventMessage aEventMessage,
+      const Maybe<ScrollableLayerGuid>& aTargetGuid) = 0;
+
+  virtual ~APZInputBridge() = default;
+};
+
+std::ostream& operator<<(std::ostream& aOut,
+                         const APZHandledResult& aHandledResult);
+
+// This enum class is used for communicating between APZ and the browser gesture
+// support code. APZ needs to wait for the browser to send this response just
+// like APZ waits for the content's response if there's an APZ ware event
+// listener in the content process.
+enum class BrowserGestureResponse : bool {
+  NotConsumed = 0,  // Representing the browser doesn't consume the gesture
+  Consumed = 1,  // Representing the browser has started consuming the gesture.
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_APZInputBridge_h
diff --git a/gfx/layers/apz/public/APZPublicUtils.h b/gfx/layers/apz/public/APZPublicUtils.h
new file mode 100644
index 0000000000..6433008b4c
--- /dev/null
+++ b/gfx/layers/apz/public/APZPublicUtils.h
@@ -0,0 +1,82 @@
+/* -*- 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 mozilla_layers_APZPublicUtils_h
+#define mozilla_layers_APZPublicUtils_h
+
+// This file is for APZ-related utilities that need to be consumed from outside
+// of gfx/layers. For internal utilities, prefer APZUtils.h.
+
+#include <stdint.h>
+#include <utility>
+#include "ScrollAnimationBezierPhysics.h"
+#include "Units.h"
+#include "mozilla/DefineEnum.h"
+#include "mozilla/ScrollOrigin.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/ScrollTypes.h"
+
+namespace mozilla {
+
+namespace layers {
+
+struct FrameMetrics;
+
+// clang-format off
+MOZ_DEFINE_ENUM_CLASS_WITH_BASE(APZWheelAction, uint8_t, (
+    Scroll,
+    PinchZoom
+))
+// clang-format on
+
+namespace apz {
+
+/**
+ * Initializes the global state used in AsyncPanZoomController.
+ * This is normally called when it is first needed in the constructor
+ * of APZCTreeManager, but can be called manually to force it to be
+ * initialized earlier.
+ */
+void InitializeGlobalState();
+
+/**
+ * See AsyncPanZoomController::CalculatePendingDisplayPort. This
+ * function simply delegates to that one, so that non-layers code
+ * never needs to include AsyncPanZoomController.h
+ */
+const ScreenMargin CalculatePendingDisplayPort(
+    const FrameMetrics& aFrameMetrics, const ParentLayerPoint& aVelocity);
+
+/**
+ * Returns a width and height multiplier, each of which is a power of two
+ * between 1 and 8 inclusive. The multiplier is chosen based on the provided
+ * base size, such that multiplier is larger when the base size is larger.
+ * The exact details are somewhat arbitrary and tuned by hand.
+ * This function is intended to only be used with WebRender, because that is
+ * the codepath that wants to use a larger displayport alignment, because
+ * moving the displayport is relatively expensive with WebRender.
+ */
+gfx::IntSize GetDisplayportAlignmentMultiplier(const ScreenSize& aBaseSize);
+
+/**
+ * Calculate the physics parameters for smooth scroll animations for the
+ * given origin, based on pref values.
+ */
+ScrollAnimationBezierPhysicsSettings ComputeBezierAnimationSettingsForOrigin(
+    ScrollOrigin aOrigin);
+
+/**
+ * Calculate if the scrolling should be instant or smooth based based on
+ * preferences and the origin
+ */
+ScrollMode GetScrollModeForOrigin(ScrollOrigin origin);
+
+}  // namespace apz
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_APZPublicUtils_h
diff --git a/gfx/layers/apz/public/APZSampler.h b/gfx/layers/apz/public/APZSampler.h
new file mode 100644
index 0000000000..a870c2d688
--- /dev/null
+++ b/gfx/layers/apz/public/APZSampler.h
@@ -0,0 +1,154 @@
+/* -*- 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 mozilla_layers_APZSampler_h
+#define mozilla_layers_APZSampler_h
+
+#include <unordered_map>
+
+#include "apz/src/APZCTreeManager.h"
+#include "base/platform_thread.h"  // for PlatformThreadId
+#include "mozilla/layers/APZUtils.h"
+#include "mozilla/layers/SampleTime.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/webrender/WebRenderTypes.h"
+#include "Units.h"
+#include "VsyncSource.h"
+
+namespace mozilla {
+
+class TimeStamp;
+
+namespace wr {
+struct Transaction;
+class TransactionWrapper;
+struct WrWindowId;
+}  // namespace wr
+
+namespace layers {
+
+struct ScrollbarData;
+
+/**
+ * This interface exposes APZ methods related to "sampling" (i.e. reading the
+ * async transforms produced by APZ). These methods should all be called on
+ * the sampler thread.
+ */
+class APZSampler {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(APZSampler)
+
+ public:
+  APZSampler(const RefPtr<APZCTreeManager>& aApz, bool aIsUsingWebRender);
+
+  // Whoever creates this sampler is responsible for calling Destroy() on it
+  // before releasing the owning refptr.
+  void Destroy();
+
+  void SetWebRenderWindowId(const wr::WindowId& aWindowId);
+
+  /**
+   * This function is invoked from rust on the render backend thread when it
+   * is created. It effectively tells the APZSampler "the current thread is
+   * the sampler thread for this window id" and allows APZSampler to remember
+   * which thread it is.
+   */
+  static void SetSamplerThread(const wr::WrWindowId& aWindowId);
+  static void SampleForWebRender(const wr::WrWindowId& aWindowId,
+                                 const uint64_t* aGeneratedFrameId,
+                                 wr::Transaction* aTransaction);
+
+  void SetSampleTime(const SampleTime& aSampleTime);
+  void SampleForWebRender(const Maybe<VsyncId>& aGeneratedFrameId,
+                          wr::TransactionWrapper& aTxn);
+
+  /**
+   * Similar to above GetCurrentAsyncTransform, but get the current transform
+   * with LayersId and ViewID.
+   * NOTE: This function should NOT be called on the compositor thread.
+   */
+  AsyncTransform GetCurrentAsyncTransform(
+      const LayersId& aLayersId, const ScrollableLayerGuid::ViewID& aScrollId,
+      AsyncTransformComponents aComponents,
+      const MutexAutoLock& aProofOfMapLock) const;
+
+  /**
+   * Returns the composition bounds of the APZC corresponding to the pair of
+   * |aLayersId| and |aScrollId|.
+   */
+  ParentLayerRect GetCompositionBounds(
+      const LayersId& aLayersId, const ScrollableLayerGuid::ViewID& aScrollId,
+      const MutexAutoLock& aProofOfMapLock) const;
+
+  struct ScrollOffsetAndRange {
+    CSSPoint mOffset;
+    CSSRect mRange;
+  };
+  /**
+   * Returns the scroll offset and scroll range of the APZC corresponding to the
+   * pair of |aLayersId| and |aScrollId|
+   *
+   * Note: This is called from OMTA Sampler thread, or Compositor thread for
+   * testing.
+   */
+  Maybe<ScrollOffsetAndRange> GetCurrentScrollOffsetAndRange(
+      const LayersId& aLayersId, const ScrollableLayerGuid::ViewID& aScrollId,
+      const MutexAutoLock& aProofOfMapLock) const;
+
+  /**
+   * This can be used to assert that the current thread is the
+   * sampler thread (which samples the async transform).
+   * This does nothing if thread assertions are disabled.
+   */
+  void AssertOnSamplerThread() const;
+
+  /**
+   * Returns true if currently on the APZSampler's "sampler thread".
+   */
+  bool IsSamplerThread() const;
+
+  template <typename Callback>
+  void CallWithMapLock(Callback& aCallback) {
+    mApz->CallWithMapLock(aCallback);
+  }
+
+ protected:
+  virtual ~APZSampler();
+
+  static already_AddRefed<APZSampler> GetSampler(
+      const wr::WrWindowId& aWindowId);
+
+ private:
+  RefPtr<APZCTreeManager> mApz;
+  bool mIsUsingWebRender;
+
+  // Used to manage the mapping from a WR window id to APZSampler. These are
+  // only used if WebRender is enabled. Both sWindowIdMap and mWindowId should
+  // only be used while holding the sWindowIdLock. Note that we use a
+  // StaticAutoPtr wrapper on sWindowIdMap to avoid a static initializer for the
+  // unordered_map. This also avoids the initializer/memory allocation in cases
+  // where we're not using WebRender.
+  static StaticMutex sWindowIdLock MOZ_UNANNOTATED;
+  static StaticAutoPtr<std::unordered_map<uint64_t, RefPtr<APZSampler>>>
+      sWindowIdMap;
+  Maybe<wr::WrWindowId> mWindowId;
+
+  // Lock used to protected mSamplerThreadId
+  mutable Mutex mThreadIdLock MOZ_UNANNOTATED;
+  // If WebRender is enabled, this holds the thread id of the render backend
+  // thread (which is the sampler thread) for the compositor associated with
+  // this APZSampler instance.
+  Maybe<PlatformThreadId> mSamplerThreadId;
+
+  Mutex mSampleTimeLock MOZ_UNANNOTATED;
+  // Can only be accessed or modified while holding mSampleTimeLock.
+  SampleTime mSampleTime;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_APZSampler_h
diff --git a/gfx/layers/apz/public/APZUpdater.h b/gfx/layers/apz/public/APZUpdater.h
new file mode 100644
index 0000000000..66d040b356
--- /dev/null
+++ b/gfx/layers/apz/public/APZUpdater.h
@@ -0,0 +1,236 @@
+/* -*- 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 mozilla_layers_APZUpdater_h
+#define mozilla_layers_APZUpdater_h
+
+#include <deque>
+#include <unordered_map>
+
+#include "base/platform_thread.h"  // for PlatformThreadId
+#include "LayersTypes.h"
+#include "mozilla/layers/APZTestData.h"
+#include "mozilla/layers/WebRenderScrollData.h"
+#include "mozilla/StaticMutex.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/webrender/WebRenderTypes.h"
+#include "nsThreadUtils.h"
+#include "Units.h"
+
+namespace mozilla {
+
+namespace layers {
+
+class APZCTreeManager;
+class FocusTarget;
+class WebRenderScrollData;
+
+/**
+ * This interface is used to send updates or otherwise mutate APZ internal
+ * state. These functions is usually called from the compositor thread in
+ * response to IPC messages. The method implementations internally redispatch
+ * themselves to the updater thread in the case where the compositor thread
+ * is not the updater thread.
+ */
+class APZUpdater {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(APZUpdater)
+
+ public:
+  APZUpdater(const RefPtr<APZCTreeManager>& aApz, bool aConnectedToWebRender);
+
+  bool HasTreeManager(const RefPtr<APZCTreeManager>& aApz);
+  void SetWebRenderWindowId(const wr::WindowId& aWindowId);
+
+  /**
+   * This function is invoked from rust on the scene builder thread when it
+   * is created. It effectively tells the APZUpdater "the current thread is
+   * the updater thread for this window id" and allows APZUpdater to remember
+   * which thread it is.
+   */
+  static void SetUpdaterThread(const wr::WrWindowId& aWindowId);
+  static void PrepareForSceneSwap(const wr::WrWindowId& aWindowId);
+  static void CompleteSceneSwap(const wr::WrWindowId& aWindowId,
+                                const wr::WrPipelineInfo& aInfo);
+  static void ProcessPendingTasks(const wr::WrWindowId& aWindowId);
+
+  void ClearTree(LayersId aRootLayersId);
+  void UpdateFocusState(LayersId aRootLayerTreeId,
+                        LayersId aOriginatingLayersId,
+                        const FocusTarget& aFocusTarget);
+  /**
+   * This should be called (in the WR-enabled case) when the compositor receives
+   * a new WebRenderScrollData for a layers id. The |aScrollData| parameter is
+   * the scroll data for |aOriginatingLayersId| and |aEpoch| is the
+   * corresponding epoch for the transaction that transferred the scroll data.
+   * This function will store the new scroll data and update the focus state and
+   * hit-testing tree.
+   */
+  void UpdateScrollDataAndTreeState(LayersId aRootLayerTreeId,
+                                    LayersId aOriginatingLayersId,
+                                    const wr::Epoch& aEpoch,
+                                    WebRenderScrollData&& aScrollData);
+  /**
+   * This is called in the WR-enabled case when we get an empty transaction that
+   * has some scroll offset updates (from paint-skipped scrolling on the content
+   * side). This function will update the stored scroll offsets and the
+   * hit-testing tree.
+   */
+  void UpdateScrollOffsets(LayersId aRootLayerTreeId,
+                           LayersId aOriginatingLayersId,
+                           ScrollUpdatesMap&& aUpdates,
+                           uint32_t aPaintSequenceNumber);
+
+  void NotifyLayerTreeAdopted(LayersId aLayersId,
+                              const RefPtr<APZUpdater>& aOldUpdater);
+  void NotifyLayerTreeRemoved(LayersId aLayersId);
+
+  bool GetAPZTestData(LayersId aLayersId, APZTestData* aOutData);
+
+  void SetTestAsyncScrollOffset(LayersId aLayersId,
+                                const ScrollableLayerGuid::ViewID& aScrollId,
+                                const CSSPoint& aOffset);
+  void SetTestAsyncZoom(LayersId aLayersId,
+                        const ScrollableLayerGuid::ViewID& aScrollId,
+                        const LayerToParentLayerScale& aZoom);
+
+  // This can only be called on the updater thread.
+  const WebRenderScrollData* GetScrollData(LayersId aLayersId) const;
+
+  /**
+   * This can be used to assert that the current thread is the
+   * updater thread (which samples the async transform).
+   * This does nothing if thread assertions are disabled.
+   */
+  void AssertOnUpdaterThread() const;
+
+  /**
+   * Runs the given task on the APZ "updater thread" for this APZUpdater. If
+   * this function is called from the updater thread itself then the task is
+   * run immediately without getting queued.
+   *
+   * The layers id argument should be the id of the layer tree that is
+   * requesting this task to be run. Conceptually each layer tree has a separate
+   * task queue, so that if one layer tree is blocked waiting for a scene build
+   * then tasks for the other layer trees can still be processed.
+   */
+  void RunOnUpdaterThread(LayersId aLayersId, already_AddRefed<Runnable> aTask);
+
+  /**
+   * Returns true if currently on the APZUpdater's "updater thread".
+   */
+  bool IsUpdaterThread() const;
+
+  /**
+   * Dispatches the given task to the APZ "controller thread", but does it
+   * *from* the updater thread. That is, if the thread on which this function is
+   * called is not the updater thread, the task is first dispatched to the
+   * updater thread. When the updater thread runs it (or if this is called
+   * directly on the updater thread), that is when the task gets dispatched to
+   * the controller thread. The controller thread then actually runs the task.
+   *
+   * See the RunOnUpdaterThread method for details on the layers id argument.
+   */
+  void RunOnControllerThread(LayersId aLayersId,
+                             already_AddRefed<Runnable> aTask);
+
+  void MarkAsDetached(LayersId aLayersId);
+
+ protected:
+  virtual ~APZUpdater();
+
+  // Return true if the APZUpdater is connected to WebRender and is
+  // using a WebRender scene builder thread as its updater thread.
+  // This is only false during GTests, and a shutdown codepath during
+  // which we create a dummy APZUpdater.
+  bool IsConnectedToWebRender() const;
+
+  static already_AddRefed<APZUpdater> GetUpdater(
+      const wr::WrWindowId& aWindowId);
+
+  void ProcessQueue();
+
+ private:
+  RefPtr<APZCTreeManager> mApz;
+  bool mDestroyed;
+  bool mConnectedToWebRender;
+
+  // Map from layers id to WebRenderScrollData. This can only be touched on
+  // the updater thread.
+  std::unordered_map<LayersId, WebRenderScrollData, LayersId::HashFn>
+      mScrollData;
+
+  // Stores epoch state for a particular layers id. This structure is only
+  // accessed on the updater thread.
+  struct EpochState {
+    // The epoch for the most recent scroll data sent from the content side.
+    wr::Epoch mRequired;
+    // The epoch for the most recent scene built and swapped in on the WR side.
+    Maybe<wr::Epoch> mBuilt;
+    // True if and only if the layers id is the root layers id for the
+    // compositor
+    bool mIsRoot;
+
+    EpochState();
+
+    // Whether or not the state for this layers id is such that it blocks
+    // processing of tasks for the layer tree. This happens if the root layers
+    // id or a "visible" layers id has scroll data for an epoch newer than what
+    // has been built. A "visible" layers id is one that is attached to the full
+    // layer tree (i.e. there is a chain of reflayer items from the root layer
+    // tree to the relevant layer subtree). This is not always the case; for
+    // instance a content process may send the compositor layers for a document
+    // before the chrome has attached the remote iframe to the root document.
+    // Since WR only builds pipelines for "visible" layers ids, |mBuilt| being
+    // populated means that the layers id is "visible".
+    bool IsBlocked() const;
+  };
+
+  // Map from layers id to epoch state.
+  // This data structure can only be touched on the updater thread.
+  std::unordered_map<LayersId, EpochState, LayersId::HashFn> mEpochData;
+
+  // Used to manage the mapping from a WR window id to APZUpdater. These are
+  // only used if WebRender is enabled. Both sWindowIdMap and mWindowId should
+  // only be used while holding the sWindowIdLock. Note that we use a
+  // StaticAutoPtr wrapper on sWindowIdMap to avoid a static initializer for the
+  // unordered_map. This also avoids the initializer/memory allocation in cases
+  // where we're not using WebRender.
+  static StaticMutex sWindowIdLock MOZ_UNANNOTATED;
+  static StaticAutoPtr<std::unordered_map<uint64_t, APZUpdater*>> sWindowIdMap;
+  Maybe<wr::WrWindowId> mWindowId;
+
+  // Lock used to protected mUpdaterThreadId;
+  mutable Mutex mThreadIdLock MOZ_UNANNOTATED;
+  // If WebRender and async scene building are enabled, this holds the thread id
+  // of the scene builder thread (which is the updater thread) for the
+  // compositor associated with this APZUpdater instance. It may be populated
+  // even if async scene building is not enabled, but in that case we don't
+  // care about the contents.
+  Maybe<PlatformThreadId> mUpdaterThreadId;
+
+  // Helper struct that pairs each queued runnable with the layers id that it is
+  // associated with. This allows us to easily implement the conceptual
+  // separation of mUpdaterQueue into independent queues per layers id.
+  struct QueuedTask {
+    LayersId mLayersId;
+    RefPtr<Runnable> mRunnable;
+  };
+
+  // Lock used to protect mUpdaterQueue
+  Mutex mQueueLock MOZ_UNANNOTATED;
+  // Holds a queue of tasks to be run on the updater thread, when the updater
+  // thread is a WebRender thread, since it won't have a message loop we can
+  // dispatch to. Note that although this is a single queue it is conceptually
+  // separated into multiple ones, one per layers id. Tasks for a given layers
+  // id will always run in FIFO order, but there is no guaranteed ordering for
+  // tasks with different layers ids.
+  std::deque<QueuedTask> mUpdaterQueue;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_APZUpdater_h
diff --git a/gfx/layers/apz/public/CompositorController.h b/gfx/layers/apz/public/CompositorController.h
new file mode 100644
index 0000000000..ad71a8faf5
--- /dev/null
+++ b/gfx/layers/apz/public/CompositorController.h
@@ -0,0 +1,33 @@
+/* -*- 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 mozilla_layers_CompositorController_h
+#define mozilla_layers_CompositorController_h
+
+#include "nsISupportsImpl.h"  // for NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+#include "mozilla/Maybe.h"
+#include "mozilla/webrender/WebRenderTypes.h"
+
+namespace mozilla {
+namespace layers {
+
+class CompositorController {
+ public:
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  /**
+   * Ask the compositor to schedule a new composite.
+   */
+  virtual void ScheduleRenderOnCompositorThread(wr::RenderReasons aReasons) = 0;
+
+ protected:
+  virtual ~CompositorController() = default;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_CompositorController_h
diff --git a/gfx/layers/apz/public/GeckoContentController.h b/gfx/layers/apz/public/GeckoContentController.h
new file mode 100644
index 0000000000..ad6246d4f8
--- /dev/null
+++ b/gfx/layers/apz/public/GeckoContentController.h
@@ -0,0 +1,189 @@
+/* -*- 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 mozilla_layers_GeckoContentController_h
+#define mozilla_layers_GeckoContentController_h
+
+#include "GeckoContentControllerTypes.h"
+#include "InputData.h"              // for PinchGestureInput
+#include "LayersTypes.h"            // for ScrollDirection
+#include "Units.h"                  // for CSSPoint, CSSRect, etc
+#include "mozilla/Assertions.h"     // for MOZ_ASSERT_HELPER2
+#include "mozilla/Attributes.h"     // for MOZ_CAN_RUN_SCRIPT
+#include "mozilla/DefineEnum.h"     // for MOZ_DEFINE_ENUM
+#include "mozilla/EventForwards.h"  // for Modifiers
+#include "mozilla/layers/APZThreadUtils.h"
+#include "mozilla/layers/MatrixMessage.h"        // for MatrixMessage
+#include "mozilla/layers/ScrollableLayerGuid.h"  // for ScrollableLayerGuid, etc
+#include "nsISupportsImpl.h"
+
+namespace mozilla {
+
+class Runnable;
+
+namespace layers {
+
+struct DoubleTapToZoomMetrics;
+struct RepaintRequest;
+
+class GeckoContentController {
+ public:
+  using APZStateChange = GeckoContentController_APZStateChange;
+  using TapType = GeckoContentController_TapType;
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(GeckoContentController)
+
+  /**
+   * Notifies the content side of the most recently computed transforms for
+   * each layers subtree to the root. The nsTArray will contain one
+   *  MatrixMessage for each layers id in the current APZ tree, along with the
+   * corresponding transform.
+   */
+  virtual void NotifyLayerTransforms(nsTArray<MatrixMessage>&& aTransforms) = 0;
+
+  /**
+   * Requests a paint of the given RepaintRequest |aRequest| from Gecko.
+   * Implementations per-platform are responsible for actually handling this.
+   *
+   * This method must always be called on the repaint thread, which depends
+   * on the GeckoContentController. For ChromeProcessController it is the
+   * Gecko main thread, while for RemoteContentController it is the compositor
+   * thread where it can send IPDL messages.
+   */
+  virtual void RequestContentRepaint(const RepaintRequest& aRequest) = 0;
+
+  /**
+   * Requests handling of a tap event. |aPoint| is in LD pixels, relative to the
+   * current scroll offset.
+   */
+  MOZ_CAN_RUN_SCRIPT
+  virtual void HandleTap(
+      TapType aType, const LayoutDevicePoint& aPoint, Modifiers aModifiers,
+      const ScrollableLayerGuid& aGuid, uint64_t aInputBlockId,
+      const Maybe<DoubleTapToZoomMetrics>& aDoubleTapTooZoomMetrics) = 0;
+
+  /**
+   * When the apz.allow_zooming pref is set to false, the APZ will not
+   * translate pinch gestures to actual zooming. Instead, it will call this
+   * method to notify gecko of the pinch gesture, and allow it to deal with it
+   * however it wishes. Note that this function is not called if the pinch is
+   * prevented by content calling preventDefault() on the touch events, or via
+   * use of the touch-action property.
+   * @param aType One of PINCHGESTURE_START, PINCHGESTURE_SCALE,
+   *        PINCHGESTURE_FINGERLIFTED, or PINCHGESTURE_END, indicating the phase
+   *        of the pinch.
+   * @param aGuid The guid of the APZ that is detecting the pinch. This is
+   *        generally the root APZC for the layers id.
+   * @param aFocusPoint The focus point of the pinch event.
+   * @param aSpanChange For the START or END event, this is always 0.
+   *        For a SCALE event, this is the difference in span between the
+   *        previous state and the new state.
+   * @param aModifiers The keyboard modifiers depressed during the pinch.
+   */
+  virtual void NotifyPinchGesture(PinchGestureInput::PinchGestureType aType,
+                                  const ScrollableLayerGuid& aGuid,
+                                  const LayoutDevicePoint& aFocusPoint,
+                                  LayoutDeviceCoord aSpanChange,
+                                  Modifiers aModifiers) = 0;
+
+  /**
+   * Schedules a runnable to run on the controller thread at some time
+   * in the future.
+   * This method must always be called on the controller thread.
+   */
+  virtual void PostDelayedTask(already_AddRefed<Runnable> aRunnable,
+                               int aDelayMs) {
+    APZThreadUtils::DelayedDispatch(std::move(aRunnable), aDelayMs);
+  }
+
+  /**
+   * Returns true if we are currently on the thread that can send repaint
+   * requests.
+   */
+  virtual bool IsRepaintThread() = 0;
+
+  /**
+   * Runs the given task on the "repaint" thread.
+   */
+  virtual void DispatchToRepaintThread(already_AddRefed<Runnable> aTask) = 0;
+
+  /**
+   * General notices of APZ state changes for consumers.
+   * |aGuid| identifies the APZC originating the state change.
+   * |aChange| identifies the type of state change
+   * |aArg| is used by some state changes to pass extra information (see
+   *        the documentation for each state change above)
+   * |aInputBlockId| is populated for the |eStartTouch| and |eEndTouch|
+   *                 state changes and identifies the input block of the
+   *                 gesture that triggers the state change.
+   */
+  virtual void NotifyAPZStateChange(const ScrollableLayerGuid& aGuid,
+                                    APZStateChange aChange, int aArg = 0,
+                                    Maybe<uint64_t> aInputBlockId = Nothing()) {
+  }
+
+  /**
+   * Notify content of a MozMouseScrollFailed event.
+   */
+  virtual void NotifyMozMouseScrollEvent(
+      const ScrollableLayerGuid::ViewID& aScrollId, const nsString& aEvent) {}
+
+  /**
+   * Notify content that the repaint requests have been flushed.
+   */
+  virtual void NotifyFlushComplete() = 0;
+
+  /**
+   * If the async scrollbar-drag initiation code kicks in on the APZ side, then
+   * we need to let content know that we are dragging the scrollbar. Otherwise,
+   * by the time the mousedown events is handled by content, the scrollthumb
+   * could already have been moved via a RequestContentRepaint message at a
+   * new scroll position, and the mousedown might end up triggering a click-to-
+   * scroll on where the thumb used to be.
+   */
+  virtual void NotifyAsyncScrollbarDragInitiated(
+      uint64_t aDragBlockId, const ScrollableLayerGuid::ViewID& aScrollId,
+      ScrollDirection aDirection) = 0;
+  virtual void NotifyAsyncScrollbarDragRejected(
+      const ScrollableLayerGuid::ViewID& aScrollId) = 0;
+
+  virtual void NotifyAsyncAutoscrollRejected(
+      const ScrollableLayerGuid::ViewID& aScrollId) = 0;
+
+  virtual void CancelAutoscroll(const ScrollableLayerGuid& aGuid) = 0;
+
+  virtual void NotifyScaleGestureComplete(const ScrollableLayerGuid& aGuid,
+                                          float aScale) = 0;
+
+  virtual void UpdateOverscrollVelocity(const ScrollableLayerGuid& aGuid,
+                                        float aX, float aY,
+                                        bool aIsRootContent) {}
+  virtual void UpdateOverscrollOffset(const ScrollableLayerGuid& aGuid,
+                                      float aX, float aY, bool aIsRootContent) {
+  }
+
+  GeckoContentController() = default;
+
+  /**
+   * Needs to be called on the main thread.
+   */
+  virtual void Destroy() {}
+
+  /**
+   * Whether this is RemoteContentController.
+   */
+  virtual bool IsRemote() { return false; }
+
+  virtual PresShell* GetTopLevelPresShell() const { return nullptr; };
+
+ protected:
+  // Protected destructor, to discourage deletion outside of Release():
+  virtual ~GeckoContentController() = default;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_GeckoContentController_h
diff --git a/gfx/layers/apz/public/GeckoContentControllerTypes.h b/gfx/layers/apz/public/GeckoContentControllerTypes.h
new file mode 100644
index 0000000000..8ab478eab5
--- /dev/null
+++ b/gfx/layers/apz/public/GeckoContentControllerTypes.h
@@ -0,0 +1,68 @@
+/* -*- 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 mozilla_layers_GeckoContentControllerTypes_h
+#define mozilla_layers_GeckoContentControllerTypes_h
+
+#include "mozilla/DefineEnum.h"
+
+namespace mozilla {
+namespace layers {
+
+// clang-format off
+MOZ_DEFINE_ENUM_CLASS(GeckoContentController_APZStateChange, (
+  /**
+   * APZ started modifying the view (including panning, zooming, and fling).
+   */
+  eTransformBegin,
+  /**
+   * APZ finished modifying the view.
+   */
+  eTransformEnd,
+  /**
+   * APZ started a touch.
+   * |aArg| is 1 if touch can be a pan, 0 otherwise.
+   */
+  eStartTouch,
+  /**
+   * APZ started a pan.
+   */
+  eStartPanning,
+  /**
+   * APZ finished processing a touch.
+   * |aArg| is 1 if touch was a click, 0 otherwise.
+   */
+  eEndTouch
+));
+// clang-format on
+
+/**
+ * Different types of tap-related events that can be sent in
+ * the HandleTap function. The names should be relatively self-explanatory.
+ * Note that the eLongTapUp will always be preceded by an eLongTap, but not
+ * all eLongTap notifications will be followed by an eLongTapUp (for instance,
+ * if the user moves their finger after triggering the long-tap but before
+ * lifting it).
+ * The difference between eDoubleTap and eSecondTap is subtle - the eDoubleTap
+ * is for an actual double-tap "gesture" while eSecondTap is for the same user
+ * input but where a double-tap gesture is not allowed. This is used to fire
+ * a click event with detail=2 to web content (similar to what a mouse double-
+ * click would do).
+ */
+// clang-format off
+MOZ_DEFINE_ENUM_CLASS(GeckoContentController_TapType, (
+  eSingleTap,
+  eDoubleTap,
+  eSecondTap,
+  eLongTap,
+  eLongTapUp
+));
+// clang-format on
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_GeckoContentControllerTypes_h
diff --git a/gfx/layers/apz/public/IAPZCTreeManager.h b/gfx/layers/apz/public/IAPZCTreeManager.h
new file mode 100644
index 0000000000..59135699a1
--- /dev/null
+++ b/gfx/layers/apz/public/IAPZCTreeManager.h
@@ -0,0 +1,151 @@
+/* -*- 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 mozilla_layers_IAPZCTreeManager_h
+#define mozilla_layers_IAPZCTreeManager_h
+
+#include <stdint.h>  // for uint64_t, uint32_t
+
+#include "mozilla/layers/LayersTypes.h"          // for TouchBehaviorFlags
+#include "mozilla/layers/ScrollableLayerGuid.h"  // for ScrollableLayerGuid, etc
+#include "mozilla/layers/ZoomConstraints.h"      // for ZoomConstraints
+#include "nsTArrayForwardDeclare.h"  // for nsTArray, nsTArray_Impl, etc
+#include "nsISupportsImpl.h"         // for MOZ_COUNT_CTOR, etc
+#include "Units.h"                   // for CSSRect, etc
+
+namespace mozilla {
+namespace layers {
+
+class APZInputBridge;
+class KeyboardMap;
+struct ZoomTarget;
+
+enum AllowedTouchBehavior {
+  NONE = 0,
+  VERTICAL_PAN = 1 << 0,
+  HORIZONTAL_PAN = 1 << 1,
+  PINCH_ZOOM = 1 << 2,
+  ANIMATING_ZOOM = 1 << 3,
+  UNKNOWN = 1 << 4
+};
+
+enum ZoomToRectBehavior : uint32_t {
+  DEFAULT_BEHAVIOR = 0,
+  DISABLE_ZOOM_OUT = 1 << 0,
+  PAN_INTO_VIEW_ONLY = 1 << 1,
+  ONLY_ZOOM_TO_DEFAULT_SCALE = 1 << 2,
+  ZOOM_TO_FOCUSED_INPUT = 1 << 3,
+};
+
+enum class BrowserGestureResponse : bool;
+
+class AsyncDragMetrics;
+struct APZHandledResult;
+
+class IAPZCTreeManager {
+  NS_INLINE_DECL_THREADSAFE_VIRTUAL_REFCOUNTING(IAPZCTreeManager)
+
+ public:
+  /**
+   * Set the keyboard shortcuts to use for translating keyboard events.
+   */
+  virtual void SetKeyboardMap(const KeyboardMap& aKeyboardMap) = 0;
+
+  /**
+   * Kicks an animation to zoom to a rect. This may be either a zoom out or zoom
+   * in. The actual animation is done on the sampler thread after being set
+   * up. |aRect| must be given in CSS pixels, relative to the document.
+   * |aFlags| is a combination of the ZoomToRectBehavior enum values.
+   */
+  virtual void ZoomToRect(const ScrollableLayerGuid& aGuid,
+                          const ZoomTarget& aZoomTarget,
+                          const uint32_t aFlags = DEFAULT_BEHAVIOR) = 0;
+
+  /**
+   * If we have touch listeners, this should always be called when we know
+   * definitively whether or not content has preventDefaulted any touch events
+   * that have come in. If |aPreventDefault| is true, any touch events in the
+   * queue will be discarded. This function must be called on the controller
+   * thread.
+   */
+  virtual void ContentReceivedInputBlock(uint64_t aInputBlockId,
+                                         bool aPreventDefault) = 0;
+
+  /**
+   * When the event regions code is enabled, this function should be invoked to
+   * to confirm the target of the input block. This is only needed in cases
+   * where the initial input event of the block hit a dispatch-to-content region
+   * but is safe to call for all input blocks. This function should always be
+   * invoked on the controller thread.
+   * The different elements in the array of targets correspond to the targets
+   * for the different touch points. In the case where the touch point has no
+   * target, or the target is not a scrollable frame, the target's |mScrollId|
+   * should be set to ScrollableLayerGuid::NULL_SCROLL_ID.
+   */
+  virtual void SetTargetAPZC(uint64_t aInputBlockId,
+                             const nsTArray<ScrollableLayerGuid>& aTargets) = 0;
+
+  /**
+   * Updates any zoom constraints contained in the <meta name="viewport"> tag.
+   * If the |aConstraints| is Nothing() then previously-provided constraints for
+   * the given |aGuid| are cleared.
+   */
+  virtual void UpdateZoomConstraints(
+      const ScrollableLayerGuid& aGuid,
+      const Maybe<ZoomConstraints>& aConstraints) = 0;
+
+  virtual void SetDPI(float aDpiValue) = 0;
+
+  /**
+   * Sets allowed touch behavior values for current touch-session for specific
+   * input block (determined by aInputBlock).
+   * Should be invoked by the widget. Each value of the aValues arrays
+   * corresponds to the different touch point that is currently active.
+   * Must be called after receiving the TOUCH_START event that starts the
+   * touch-session.
+   * This must be called on the controller thread.
+   */
+  virtual void SetAllowedTouchBehavior(
+      uint64_t aInputBlockId, const nsTArray<TouchBehaviorFlags>& aValues) = 0;
+
+  virtual void SetBrowserGestureResponse(uint64_t aInputBlockId,
+                                         BrowserGestureResponse aResponse) = 0;
+
+  virtual void StartScrollbarDrag(const ScrollableLayerGuid& aGuid,
+                                  const AsyncDragMetrics& aDragMetrics) = 0;
+
+  virtual bool StartAutoscroll(const ScrollableLayerGuid& aGuid,
+                               const ScreenPoint& aAnchorLocation) = 0;
+
+  virtual void StopAutoscroll(const ScrollableLayerGuid& aGuid) = 0;
+
+  /**
+   * Function used to disable LongTap gestures.
+   *
+   * On slow running tests, drags and touch events can be misinterpreted
+   * as a long tap. This allows tests to disable long tap gesture detection.
+   */
+  virtual void SetLongTapEnabled(bool aTapGestureEnabled) = 0;
+
+  /**
+   * Returns an APZInputBridge interface that can be used to send input
+   * events to APZ in a synchronous manner. This will always be non-null, and
+   * the returned object's lifetime will match the lifetime of this
+   * IAPZCTreeManager implementation.
+   * It is only valid to call this function in the UI process.
+   */
+  virtual APZInputBridge* InputBridge() = 0;
+
+ protected:
+  // Discourage destruction outside of decref
+
+  virtual ~IAPZCTreeManager() = default;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_IAPZCTreeManager_h
diff --git a/gfx/layers/apz/public/MatrixMessage.h b/gfx/layers/apz/public/MatrixMessage.h
new file mode 100644
index 0000000000..45050f7406
--- /dev/null
+++ b/gfx/layers/apz/public/MatrixMessage.h
@@ -0,0 +1,64 @@
+/* -*- 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 mozilla_layers_MatrixMessage_h
+#define mozilla_layers_MatrixMessage_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/gfx/Matrix.h"
+#include "mozilla/layers/LayersTypes.h"
+#include "Units.h"  // for ScreenRect
+#include "UnitTransforms.h"
+
+namespace mozilla {
+namespace layers {
+class MatrixMessage {
+ public:
+  // Don't use this one directly
+  MatrixMessage() = default;
+
+  MatrixMessage(const Maybe<LayerToScreenMatrix4x4>& aMatrix,
+                const ScreenRect& aTopLevelViewportVisibleRectInBrowserCoords,
+                const LayersId& aLayersId)
+      : mMatrix(ToUnknownMatrix(aMatrix)),
+        mTopLevelViewportVisibleRectInBrowserCoords(
+            aTopLevelViewportVisibleRectInBrowserCoords),
+        mLayersId(aLayersId) {}
+
+  inline Maybe<LayerToScreenMatrix4x4> GetMatrix() const {
+    return LayerToScreenMatrix4x4::FromUnknownMatrix(mMatrix);
+  }
+
+  inline ScreenRect GetTopLevelViewportVisibleRectInBrowserCoords() const {
+    return mTopLevelViewportVisibleRectInBrowserCoords;
+  }
+
+  inline const LayersId& GetLayersId() const { return mLayersId; }
+
+  bool operator==(const MatrixMessage& aOther) const {
+    return aOther.mMatrix == mMatrix &&
+           aOther.mTopLevelViewportVisibleRectInBrowserCoords ==
+               mTopLevelViewportVisibleRectInBrowserCoords &&
+           aOther.mLayersId == mLayersId;
+  }
+
+  bool operator!=(const MatrixMessage& aOther) const {
+    return !(*this == aOther);
+  }
+  // Fields are public for IPC. Don't access directly
+  // elsewhere.
+  // Transform matrix to convert this layer to screen coordinate.
+  Maybe<gfx::Matrix4x4> mMatrix;  // Untyped for IPC
+  // The remote iframe document rectangle corresponding to this layer.
+  // The rectangle is the result of clipped out by ancestor async scrolling so
+  // that the rectangle will be empty if it's completely scrolled out of view.
+  ScreenRect mTopLevelViewportVisibleRectInBrowserCoords;
+  LayersId mLayersId;
+};
+};  // namespace layers
+};  // namespace mozilla
+
+#endif  // mozilla_layers_MatrixMessage_h