diff --git a/dom/ipc/ContentChild.cpp b/dom/ipc/ContentChild.cpp
index af60d709fcdd..df6eaa6d1a64 100644
--- a/dom/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -48,7 +48,6 @@
 #include "mozilla/jsipc/CrossProcessObjectWrappers.h"
 #include "mozilla/layers/APZChild.h"
 #include "mozilla/layers/CompositorBridgeChild.h"
-#include "mozilla/layers/ContentProcessController.h"
 #include "mozilla/layers/ImageBridgeChild.h"
 #include "mozilla/layers/SharedBufferManagerChild.h"
 #include "mozilla/layout/RenderFrameChild.h"
@@ -1382,7 +1381,7 @@ ContentChild::RecvSetProcessSandbox(const MaybeFileDesc& aBroker)
 bool
 ContentChild::RecvNotifyLayerAllocated(const dom::TabId& aTabId, const uint64_t& aLayersId)
 {
-  APZChild* apz = ContentProcessController::Create(aTabId);
+  APZChild* apz = APZChild::Create(aTabId);
   return CompositorBridgeChild::Get()->SendPAPZConstructor(apz, aLayersId);
 }
 
diff --git a/dom/ipc/PBrowser.ipdl b/dom/ipc/PBrowser.ipdl
index 446a9a1b4165..6c9ae1d9438c 100644
--- a/dom/ipc/PBrowser.ipdl
+++ b/dom/ipc/PBrowser.ipdl
@@ -670,6 +670,11 @@ child:
                    int32_t aModifiers,
                    bool aPreventDefault);
 
+    /**
+     * APZ notification for mouse scroll testing events.
+     */
+    async MouseScrollTestEvent(uint64_t aLayersId, ViewID aScrollId, nsString aEvent);
+
     async CompositionEvent(WidgetCompositionEvent event);
 
     async SelectionEvent(WidgetSelectionEvent event);
diff --git a/dom/ipc/TabChild.cpp b/dom/ipc/TabChild.cpp
index f606c85750e2..9f83ea70b1f5 100644
--- a/dom/ipc/TabChild.cpp
+++ b/dom/ipc/TabChild.cpp
@@ -29,7 +29,6 @@
 #include "mozilla/layers/APZCCallbackHelper.h"
 #include "mozilla/layers/APZCTreeManager.h"
 #include "mozilla/layers/APZEventState.h"
-#include "mozilla/layers/ContentProcessController.h"
 #include "mozilla/layers/CompositorBridgeChild.h"
 #include "mozilla/layers/DoubleTapToZoom.h"
 #include "mozilla/layers/ImageBridgeChild.h"
@@ -1939,6 +1938,26 @@ TabChild::RecvMouseWheelEvent(const WidgetWheelEvent& aEvent,
   return true;
 }
 
+bool
+TabChild::RecvMouseScrollTestEvent(const uint64_t& aLayersId,
+                                   const FrameMetrics::ViewID& aScrollId, const nsString& aEvent)
+{
+  if (aLayersId != mLayersId) {
+    RefPtr<TabParent> browser = TabParent::GetTabParentFromLayersId(aLayersId);
+    if (!browser) {
+      return false;
+    }
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+      [aLayersId, browser, aScrollId, aEvent] () -> void {
+        Unused << browser->SendMouseScrollTestEvent(aLayersId, aScrollId, aEvent);
+      }));
+    return true;
+  }
+
+  APZCCallbackHelper::NotifyMozMouseScrollEvent(aScrollId, aEvent);
+  return true;
+}
+
 bool
 TabChild::RecvRealTouchEvent(const WidgetTouchEvent& aEvent,
                              const ScrollableLayerGuid& aGuid,
diff --git a/dom/ipc/TabChild.h b/dom/ipc/TabChild.h
index aaa71b84bbab..29a720c88d01 100644
--- a/dom/ipc/TabChild.h
+++ b/dom/ipc/TabChild.h
@@ -388,6 +388,10 @@ public:
                             const int32_t& aModifiers,
                             const bool& aPreventDefault) override;
 
+  virtual bool RecvMouseScrollTestEvent(const uint64_t& aLayersId,
+                                        const FrameMetrics::ViewID& aScrollId,
+                                        const nsString& aEvent) override;
+
   virtual bool RecvNativeSynthesisResponse(const uint64_t& aObserverId,
                                            const nsCString& aResponse) override;
 
diff --git a/gfx/layers/apz/util/ContentProcessController.cpp b/gfx/layers/apz/util/ContentProcessController.cpp
deleted file mode 100644
index 37e67350331b..000000000000
--- a/gfx/layers/apz/util/ContentProcessController.cpp
+++ /dev/null
@@ -1,200 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set sw=4 ts=8 et 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 "ContentProcessController.h"
-
-#include "mozilla/dom/TabChild.h"
-#include "mozilla/layers/APZCCallbackHelper.h"
-#include "mozilla/layers/APZChild.h"
-
-#include "InputData.h"                  // for InputData
-
-namespace mozilla {
-namespace layers {
-
-/**
- * There are cases where we try to create the APZChild before the corresponding
- * TabChild has been created, we use an observer for the "tab-child-created"
- * topic to set the TabChild in the APZChild when it has been created.
- */
-class TabChildCreatedObserver : public nsIObserver
-{
-public:
-  TabChildCreatedObserver(ContentProcessController* aController, const dom::TabId& aTabId)
-    : mController(aController),
-      mTabId(aTabId)
-  {}
-
-  NS_DECL_ISUPPORTS
-  NS_DECL_NSIOBSERVER
-
-private:
-  virtual ~TabChildCreatedObserver()
-  {}
-
-  // TabChildCreatedObserver is owned by mController, and mController outlives its
-  // TabChildCreatedObserver, so the raw pointer is fine.
-  ContentProcessController* mController;
-  dom::TabId mTabId;
-};
-
-NS_IMPL_ISUPPORTS(TabChildCreatedObserver, nsIObserver)
-
-NS_IMETHODIMP
-TabChildCreatedObserver::Observe(nsISupports* aSubject,
-                                 const char* aTopic,
-                                 const char16_t* aData)
-{
-  MOZ_ASSERT(strcmp(aTopic, "tab-child-created") == 0);
-
-  nsCOMPtr<nsITabChild> tabChild(do_QueryInterface(aSubject));
-  NS_ENSURE_TRUE(tabChild, NS_ERROR_FAILURE);
-
-  dom::TabChild* browser = static_cast<dom::TabChild*>(tabChild.get());
-
-  if (browser->GetTabId() == mTabId) {
-    mController->SetBrowser(browser);
-  }
-  return NS_OK;
-}
-
-APZChild*
-ContentProcessController::Create(const dom::TabId& aTabId)
-{
-  RefPtr<dom::TabChild> browser = dom::TabChild::FindTabChild(aTabId);
-
-  ContentProcessController* controller = new ContentProcessController();
-
-  nsAutoPtr<APZChild> apz(new APZChild(controller));
-
-  if (browser) {
-
-    controller->SetBrowser(browser);
-
-  } else {
-
-    RefPtr<TabChildCreatedObserver> observer =
-      new TabChildCreatedObserver(controller, aTabId);
-    nsCOMPtr<nsIObserverService> os = services::GetObserverService();
-    if (!os ||
-        NS_FAILED(os->AddObserver(observer, "tab-child-created", false))) {
-      return nullptr;
-    }
-    controller->SetObserver(observer);
-
-  }
-
-  return apz.forget();
-}
-
-ContentProcessController::ContentProcessController()
-    : mBrowser(nullptr)
-{
-}
-ContentProcessController::~ContentProcessController()
-{
-  if (mObserver) {
-    nsCOMPtr<nsIObserverService> os = services::GetObserverService();
-    os->RemoveObserver(mObserver, "tab-child-created");
-  } else if (mBrowser) {
-    mBrowser->SetAPZChild(nullptr);
-  }
-}
-
-void
-ContentProcessController::SetObserver(nsIObserver* aObserver)
-{
-  MOZ_ASSERT(!mBrowser);
-  mObserver = aObserver;
-}
-
-void
-ContentProcessController::SetBrowser(dom::TabChild* aBrowser)
-{
-  MOZ_ASSERT(!mBrowser);
-  mBrowser = aBrowser;
-
-  if (mObserver) {
-    nsCOMPtr<nsIObserverService> os = services::GetObserverService();
-    os->RemoveObserver(mObserver, "tab-child-created");
-    mObserver = nullptr;
-  }
-}
-void
-ContentProcessController::RequestContentRepaint(const FrameMetrics& aFrameMetrics)
-{
-  if (mBrowser) {
-    mBrowser->UpdateFrame(aFrameMetrics);
-  }
-}
-
-void
-ContentProcessController::HandleTap(
-                        TapType aType,
-                        const LayoutDevicePoint& aPoint,
-                        Modifiers aModifiers,
-                        const ScrollableLayerGuid& aGuid,
-                        uint64_t aInputBlockId)
-{
-  if (mBrowser) {
-    mBrowser->HandleTap(aType, aPoint - mBrowser->GetChromeDisplacement(), aModifiers, aGuid,
-        aInputBlockId, (aType == TapType::eSingleTap));
-  }
-}
-
-void
-ContentProcessController::NotifyAPZStateChange(
-                                  const ScrollableLayerGuid& aGuid,
-                                  APZStateChange aChange,
-                                  int aArg)
-{
-  if (mBrowser) {
-    mBrowser->NotifyAPZStateChange(aGuid.mScrollId, aChange, aArg);
-  }
-}
-
-void
-ContentProcessController::NotifyMozMouseScrollEvent(
-                                  const FrameMetrics::ViewID& aScrollId,
-                                  const nsString& aEvent)
-{
-  if (mBrowser) {
-    APZCCallbackHelper::NotifyMozMouseScrollEvent(aScrollId, aEvent);
-  }
-}
-
-void
-ContentProcessController::NotifyFlushComplete()
-{
-  if (mBrowser) {
-    nsCOMPtr<nsIPresShell> shell;
-    if (nsCOMPtr<nsIDocument> doc = mBrowser->GetDocument()) {
-      shell = doc->GetShell();
-    }
-    APZCCallbackHelper::NotifyFlushComplete(shell.get());
-  }
-}
-
-void
-ContentProcessController::PostDelayedTask(already_AddRefed<Runnable> aRunnable, int aDelayMs)
-{
-  MOZ_ASSERT_UNREACHABLE("ContentProcessController should only be used remotely.");
-}
-
-bool
-ContentProcessController::IsRepaintThread()
-{
-  return NS_IsMainThread();
-}
-
-void
-ContentProcessController::DispatchToRepaintThread(already_AddRefed<Runnable> aTask)
-{
-  NS_DispatchToMainThread(Move(aTask));
-}
-
-} // namespace layers
-} // namespace mozilla
diff --git a/gfx/layers/apz/util/ContentProcessController.h b/gfx/layers/apz/util/ContentProcessController.h
deleted file mode 100644
index 2fb24262571d..000000000000
--- a/gfx/layers/apz/util/ContentProcessController.h
+++ /dev/null
@@ -1,74 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set sw=4 ts=8 et 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_ContentProcessController_h
-#define mozilla_layers_ContentProcessController_h
-
-#include "mozilla/layers/GeckoContentController.h"
-
-class nsIObserver;
-
-namespace mozilla {
-
-namespace dom {
-class TabChild;
-} // namespace dom
-
-namespace layers {
-
-class APZChild;
-
-class ContentProcessController final
-      : public GeckoContentController
-{
-public:
-  ~ContentProcessController();
-
-  static APZChild* Create(const dom::TabId& aTabId);
-
-  // ContentProcessController
-
-  void SetBrowser(dom::TabChild* aBrowser);
-
-  // GeckoContentController
-
-  void RequestContentRepaint(const FrameMetrics& frame) override;
-
-  void HandleTap(TapType aType,
-                 const LayoutDevicePoint& aPoint,
-                 Modifiers aModifiers,
-                 const ScrollableLayerGuid& aGuid,
-                 uint64_t aInputBlockId) override;
-
-  void NotifyAPZStateChange(const ScrollableLayerGuid& aGuid,
-                            APZStateChange aChange,
-                            int aArg) override;
-
-  void NotifyMozMouseScrollEvent(const FrameMetrics::ViewID& aScrollId,
-                                 const nsString& aEvent) override;
-
-  void NotifyFlushComplete() override;
-
-  void PostDelayedTask(already_AddRefed<Runnable> aRunnable, int aDelayMs) override;
-
-  bool IsRepaintThread() override;
-
-  void DispatchToRepaintThread(already_AddRefed<Runnable> aTask) override;
-
-private:
-  ContentProcessController();
-
-  void SetObserver(nsIObserver* aObserver);
-
-  RefPtr<dom::TabChild> mBrowser;
-  RefPtr<nsIObserver> mObserver;
-};
-
-} // namespace layers
-
-} // namespace mozilla
-
-#endif // mozilla_layers_ContentProcessController_h
diff --git a/gfx/layers/ipc/APZChild.cpp b/gfx/layers/ipc/APZChild.cpp
index cf59f08fd198..620847196b18 100644
--- a/gfx/layers/ipc/APZChild.cpp
+++ b/gfx/layers/ipc/APZChild.cpp
@@ -5,37 +5,98 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/layers/APZChild.h"
-#include "mozilla/layers/GeckoContentController.h"
 
 #include "mozilla/dom/TabChild.h"
 #include "mozilla/layers/APZCCallbackHelper.h"
 
-#include "InputData.h" // for InputData
-
 namespace mozilla {
 namespace layers {
 
-APZChild::APZChild(RefPtr<GeckoContentController> aController)
-  : mController(aController)
+/**
+ * There are cases where we try to create the APZChild before the corresponding
+ * TabChild has been created, we use an observer for the "tab-child-created"
+ * topic to set the TabChild in the APZChild when it has been created.
+ */
+class TabChildCreatedObserver : public nsIObserver
+{
+public:
+  TabChildCreatedObserver(APZChild* aAPZChild, const dom::TabId& aTabId)
+    : mAPZChild(aAPZChild),
+      mTabId(aTabId)
+  {}
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+private:
+  virtual ~TabChildCreatedObserver()
+  {}
+
+  // TabChildCreatedObserver is owned by mAPZChild, and mAPZChild outlives its
+  // TabChildCreatedObserver, so the raw pointer is fine.
+  APZChild* mAPZChild;
+  dom::TabId mTabId;
+};
+
+NS_IMPL_ISUPPORTS(TabChildCreatedObserver, nsIObserver)
+
+NS_IMETHODIMP
+TabChildCreatedObserver::Observe(nsISupports* aSubject,
+                                 const char* aTopic,
+                                 const char16_t* aData)
+{
+  MOZ_ASSERT(strcmp(aTopic, "tab-child-created") == 0);
+
+  nsCOMPtr<nsITabChild> tabChild(do_QueryInterface(aSubject));
+  NS_ENSURE_TRUE(tabChild, NS_ERROR_FAILURE);
+
+  dom::TabChild* browser = static_cast<dom::TabChild*>(tabChild.get());
+  if (browser->GetTabId() == mTabId) {
+    mAPZChild->SetBrowser(browser);
+  }
+  return NS_OK;
+}
+
+APZChild*
+APZChild::Create(const dom::TabId& aTabId)
+{
+  RefPtr<dom::TabChild> browser = dom::TabChild::FindTabChild(aTabId);
+  nsAutoPtr<APZChild> apz(new APZChild);
+  if (browser) {
+    apz->SetBrowser(browser);
+  } else {
+    RefPtr<TabChildCreatedObserver> observer =
+      new TabChildCreatedObserver(apz, aTabId);
+    nsCOMPtr<nsIObserverService> os = services::GetObserverService();
+    if (!os ||
+        NS_FAILED(os->AddObserver(observer, "tab-child-created", false))) {
+      return nullptr;
+    }
+    apz->SetObserver(observer);
+  }
+
+  return apz.forget();
+}
+
+APZChild::APZChild()
+  : mDestroyed(false)
 {
-  MOZ_ASSERT(mController);
 }
 
 APZChild::~APZChild()
 {
-  if (mController) {
-    mController->Destroy();
-    mController = nullptr;
+  if (mObserver) {
+    nsCOMPtr<nsIObserverService> os = services::GetObserverService();
+    os->RemoveObserver(mObserver, "tab-child-created");
+  } else if (mBrowser) {
+    mBrowser->SetAPZChild(nullptr);
   }
 }
 
 bool
 APZChild::RecvRequestContentRepaint(const FrameMetrics& aFrameMetrics)
 {
-  MOZ_ASSERT(mController->IsRepaintThread());
-
-  mController->RequestContentRepaint(aFrameMetrics);
-  return true;
+  return mBrowser->UpdateFrame(aFrameMetrics);
 }
 
 bool
@@ -46,66 +107,77 @@ APZChild::RecvHandleTap(const TapType& aType,
                         const uint64_t& aInputBlockId,
                         const bool& aCallTakeFocusForClickFromTap)
 {
-  mController->HandleTap(aType, aPoint, aModifiers, aGuid,
-      aInputBlockId);
+  mBrowser->HandleTap(aType, aPoint - mBrowser->GetChromeDisplacement(), aModifiers, aGuid,
+      aInputBlockId, aCallTakeFocusForClickFromTap);
   return true;
 }
 
 bool
-APZChild::RecvUpdateOverscrollVelocity(const float& aX, const float& aY, const bool& aIsRootContent)
-{
-  mController->UpdateOverscrollVelocity(aX, aY, aIsRootContent);
-  return true;
-}
-
-bool
-APZChild::RecvUpdateOverscrollOffset(const float& aX, const float& aY, const bool& aIsRootContent)
-{
-  mController->UpdateOverscrollOffset(aX, aY, aIsRootContent);
-  return true;
-}
-
-bool
-APZChild::RecvSetScrollingRootContent(const bool& aIsRootContent)
-{
-  mController->SetScrollingRootContent(aIsRootContent);
-  return true;
-}
-
-bool
-APZChild::RecvNotifyMozMouseScrollEvent(const ViewID& aScrollId,
+APZChild::RecvNotifyMozMouseScrollEvent(const uint64_t& aLayersId,
+                                        const ViewID& aScrollId,
                                         const nsString& aEvent)
 {
-  mController->NotifyMozMouseScrollEvent(aScrollId, aEvent);
+  if (mBrowser) {
+    mBrowser->RecvMouseScrollTestEvent(aLayersId, aScrollId, aEvent);
+  }
   return true;
 }
 
 bool
-APZChild::RecvNotifyAPZStateChange(const ScrollableLayerGuid& aGuid,
+APZChild::RecvNotifyAPZStateChange(const ViewID& aViewId,
                                    const APZStateChange& aChange,
                                    const int& aArg)
 {
-  mController->NotifyAPZStateChange(aGuid, aChange, aArg);
-  return true;
+  return mBrowser->NotifyAPZStateChange(aViewId, aChange, aArg);
 }
 
 bool
 APZChild::RecvNotifyFlushComplete()
 {
-  MOZ_ASSERT(mController->IsRepaintThread());
-
-  mController->NotifyFlushComplete();
+  nsCOMPtr<nsIPresShell> shell;
+  if (nsCOMPtr<nsIDocument> doc = mBrowser->GetDocument()) {
+    shell = doc->GetShell();
+  }
+  APZCCallbackHelper::NotifyFlushComplete(shell.get());
   return true;
 }
 
 bool
 APZChild::RecvDestroy()
 {
-  // mController->Destroy will be called in the destructor
+  mDestroyed = true;
+  if (mBrowser) {
+    mBrowser->SetAPZChild(nullptr);
+    mBrowser = nullptr;
+  }
   PAPZChild::Send__delete__(this);
   return true;
 }
 
+void
+APZChild::SetObserver(nsIObserver* aObserver)
+{
+  MOZ_ASSERT(!mBrowser);
+  mObserver = aObserver;
+}
+
+void
+APZChild::SetBrowser(dom::TabChild* aBrowser)
+{
+  MOZ_ASSERT(!mBrowser);
+  if (mObserver) {
+    nsCOMPtr<nsIObserverService> os = services::GetObserverService();
+    os->RemoveObserver(mObserver, "tab-child-created");
+    mObserver = nullptr;
+  }
+  // We might get the tab-child-created notification after we receive a
+  // Destroy message from the parent. In that case we don't want to install
+  // ourselves with the browser.
+  if (!mDestroyed) {
+    mBrowser = aBrowser;
+    mBrowser->SetAPZChild(this);
+  }
+}
 
 } // namespace layers
 } // namespace mozilla
diff --git a/gfx/layers/ipc/APZChild.h b/gfx/layers/ipc/APZChild.h
index 44cb8a2d21a0..ef5655dc3c89 100644
--- a/gfx/layers/ipc/APZChild.h
+++ b/gfx/layers/ipc/APZChild.h
@@ -9,18 +9,25 @@
 
 #include "mozilla/layers/PAPZChild.h"
 
+class nsIObserver;
+
 namespace mozilla {
 
-namespace layers {
+namespace dom {
+class TabChild;
+} // namespace dom
 
-class GeckoContentController;
+namespace layers {
 
 class APZChild final : public PAPZChild
 {
 public:
-  explicit APZChild(RefPtr<GeckoContentController> aController);
+  static APZChild* Create(const dom::TabId& aTabId);
+
   ~APZChild();
 
+  void SetBrowser(dom::TabChild* aBrowser);
+
   bool RecvRequestContentRepaint(const FrameMetrics& frame) override;
 
   bool RecvHandleTap(const TapType& aType,
@@ -30,16 +37,11 @@ public:
                      const uint64_t& aInputBlockId,
                      const bool& aCallTakeFocusForClickFromTap) override;
 
-  bool RecvUpdateOverscrollVelocity(const float& aX, const float& aY, const bool& aIsRootContent) override;
-
-  bool RecvUpdateOverscrollOffset(const float& aX, const float& aY, const bool& aIsRootContent) override;
-
-  bool RecvSetScrollingRootContent(const bool& aIsRootContent) override;
-
-  bool RecvNotifyMozMouseScrollEvent(const ViewID& aScrollId,
+  bool RecvNotifyMozMouseScrollEvent(const uint64_t& aLayersId,
+                                     const ViewID& aScrollId,
                                      const nsString& aEvent) override;
 
-  bool RecvNotifyAPZStateChange(const ScrollableLayerGuid& aGuid,
+  bool RecvNotifyAPZStateChange(const ViewID& aViewId,
                                 const APZStateChange& aChange,
                                 const int& aArg) override;
 
@@ -48,7 +50,13 @@ public:
   bool RecvDestroy() override;
 
 private:
-  RefPtr<GeckoContentController> mController;
+  APZChild();
+
+  void SetObserver(nsIObserver* aObserver);
+
+  RefPtr<dom::TabChild> mBrowser;
+  RefPtr<nsIObserver> mObserver;
+  bool mDestroyed;
 };
 
 } // namespace layers
diff --git a/gfx/layers/ipc/CompositorBridgeParent.cpp b/gfx/layers/ipc/CompositorBridgeParent.cpp
index 1e003e1d18a4..b4083790a402 100644
--- a/gfx/layers/ipc/CompositorBridgeParent.cpp
+++ b/gfx/layers/ipc/CompositorBridgeParent.cpp
@@ -2584,7 +2584,7 @@ CrossProcessCompositorBridgeParent::AllocPAPZParent(const uint64_t& aLayersId)
     return nullptr;
   }
 
-  RemoteContentController* controller = new RemoteContentController();
+  RemoteContentController* controller = new RemoteContentController(aLayersId);
 
   // Increment the controller's refcount before we return it. This will keep the
   // controller alive until it is released by IPDL in DeallocPAPZParent.
diff --git a/gfx/layers/ipc/PAPZ.ipdl b/gfx/layers/ipc/PAPZ.ipdl
index befcb5e72bef..7fe516240325 100644
--- a/gfx/layers/ipc/PAPZ.ipdl
+++ b/gfx/layers/ipc/PAPZ.ipdl
@@ -57,15 +57,9 @@ child:
                   ScrollableLayerGuid aGuid, uint64_t aInputBlockId,
                   bool aCallTakeFocusForClickFromTap);
 
-  async UpdateOverscrollVelocity(float aX, float aY, bool aIsRootContent);
+  async NotifyMozMouseScrollEvent(uint64_t aLayersId, ViewID aScrollId, nsString aEvent);
 
-  async UpdateOverscrollOffset(float aX, float aY, bool aIsRootContent);
-
-  async SetScrollingRootContent(bool aIsRootContent);
-
-  async NotifyMozMouseScrollEvent(ViewID aScrollId, nsString aEvent);
-
-  async NotifyAPZStateChange(ScrollableLayerGuid aGuid, APZStateChange aChange, int aArg);
+  async NotifyAPZStateChange(ViewID aViewId, APZStateChange aChange, int aArg);
 
   async NotifyFlushComplete();
 
diff --git a/gfx/layers/ipc/RemoteContentController.cpp b/gfx/layers/ipc/RemoteContentController.cpp
index ea6ecacee814..f7bacfe3cb82 100644
--- a/gfx/layers/ipc/RemoteContentController.cpp
+++ b/gfx/layers/ipc/RemoteContentController.cpp
@@ -26,8 +26,9 @@ namespace layers {
 
 using namespace mozilla::gfx;
 
-RemoteContentController::RemoteContentController()
+RemoteContentController::RemoteContentController(uint64_t aLayersId)
   : mCompositorThread(MessageLoop::current())
+  , mLayersId(aLayersId)
   , mCanSend(true)
   , mMutex("RemoteContentController")
 {
@@ -123,48 +124,10 @@ RemoteContentController::NotifyAPZStateChange(const ScrollableLayerGuid& aGuid,
   }
 
   if (mCanSend) {
-    Unused << SendNotifyAPZStateChange(aGuid, aChange, aArg);
+    Unused << SendNotifyAPZStateChange(aGuid.mScrollId, aChange, aArg);
   }
 }
 
-void
-RemoteContentController::UpdateOverscrollVelocity(float aX, float aY, bool aIsRootContent)
-{
-  if (MessageLoop::current() != mCompositorThread) {
-    mCompositorThread->PostTask(NewRunnableMethod<float,
-                                        float, bool>(this,
-                                             &RemoteContentController::UpdateOverscrollVelocity,
-                                             aX, aY, aIsRootContent));
-    return;
-  }
-  Unused << SendUpdateOverscrollVelocity(aX, aY, aIsRootContent);
-}
-
-void
-RemoteContentController::UpdateOverscrollOffset(float aX, float aY, bool aIsRootContent)
-{
-  if (MessageLoop::current() != mCompositorThread) {
-    mCompositorThread->PostTask(NewRunnableMethod<float,
-                                        float, bool>(this,
-                                             &RemoteContentController::UpdateOverscrollOffset,
-                                             aX, aY, aIsRootContent));
-    return;
-  }
-  Unused << SendUpdateOverscrollOffset(aX, aY, aIsRootContent);
-}
-
-void
-RemoteContentController::SetScrollingRootContent(bool aIsRootContent)
-{
-  if (MessageLoop::current() != mCompositorThread) {
-    mCompositorThread->PostTask(NewRunnableMethod<bool>(this,
-                                             &RemoteContentController::SetScrollingRootContent,
-                                             aIsRootContent));
-    return;
-  }
-  Unused << SendSetScrollingRootContent(aIsRootContent);
-}
-
 void
 RemoteContentController::NotifyMozMouseScrollEvent(const FrameMetrics::ViewID& aScrollId,
                                                    const nsString& aEvent)
@@ -179,7 +142,7 @@ RemoteContentController::NotifyMozMouseScrollEvent(const FrameMetrics::ViewID& a
   }
 
   if (mCanSend) {
-    Unused << SendNotifyMozMouseScrollEvent(aScrollId, aEvent);
+    Unused << SendNotifyMozMouseScrollEvent(mLayersId, aScrollId, aEvent);
   }
 }
 
diff --git a/gfx/layers/ipc/RemoteContentController.h b/gfx/layers/ipc/RemoteContentController.h
index 9a05aa6b8c2e..fc0e27efb5b4 100644
--- a/gfx/layers/ipc/RemoteContentController.h
+++ b/gfx/layers/ipc/RemoteContentController.h
@@ -33,7 +33,7 @@ class RemoteContentController : public GeckoContentController
   using GeckoContentController::APZStateChange;
 
 public:
-  RemoteContentController();
+  explicit RemoteContentController(uint64_t aLayersId);
 
   virtual ~RemoteContentController();
 
@@ -57,12 +57,6 @@ public:
                                     APZStateChange aChange,
                                     int aArg) override;
 
-  virtual void UpdateOverscrollVelocity(float aX, float aY, bool aIsRootContent) override;
-
-  virtual void UpdateOverscrollOffset(float aX, float aY, bool aIsRootContent) override;
-
-  virtual void SetScrollingRootContent(bool aIsRootContent) override;
-
   virtual void NotifyMozMouseScrollEvent(const FrameMetrics::ViewID& aScrollId,
                                          const nsString& aEvent) override;
 
@@ -76,6 +70,7 @@ public:
 
 private:
   MessageLoop* mCompositorThread;
+  uint64_t mLayersId;
   bool mCanSend;
 
   // Mutex protecting members below accessed from multiple threads.
diff --git a/gfx/layers/ipc/SharedBufferManagerParent.cpp b/gfx/layers/ipc/SharedBufferManagerParent.cpp
index ec00239ee0bd..b019578bd2a3 100644
--- a/gfx/layers/ipc/SharedBufferManagerParent.cpp
+++ b/gfx/layers/ipc/SharedBufferManagerParent.cpp
@@ -13,7 +13,6 @@
 #include "mozilla/ipc/MessageChannel.h" // for MessageChannel, etc
 #include "mozilla/ipc/ProtocolUtils.h"
 #include "mozilla/ipc/Transport.h"      // for Transport
-#include "mozilla/Sprintf.h"
 #include "mozilla/UniquePtr.h"          // for UniquePtr
 #include "mozilla/Unused.h"
 #include "nsIMemoryReporter.h"
diff --git a/gfx/layers/moz.build b/gfx/layers/moz.build
index 4894b46da4ff..732449437002 100644
--- a/gfx/layers/moz.build
+++ b/gfx/layers/moz.build
@@ -112,7 +112,6 @@ EXPORTS.mozilla.layers += [
     'apz/util/APZEventState.h',
     'apz/util/APZThreadUtils.h',
     'apz/util/ChromeProcessController.h',
-    'apz/util/ContentProcessController.h',
     'apz/util/DoubleTapToZoom.h',
     'apz/util/InputAPZContext.h',
     'apz/util/ScrollInputMethods.h',
@@ -289,7 +288,6 @@ UNIFIED_SOURCES += [
     'apz/util/APZThreadUtils.cpp',
     'apz/util/CheckerboardReportService.cpp',
     'apz/util/ChromeProcessController.cpp',
-    'apz/util/ContentProcessController.cpp',
     'apz/util/DoubleTapToZoom.cpp',
     'apz/util/InputAPZContext.cpp',
     'apz/util/ScrollLinkedEffectDetector.cpp',