--- a/gfx/layers/apz/src/APZCTreeManager.cpp
+++ b/gfx/layers/apz/src/APZCTreeManager.cpp
@@ -1886,16 +1886,21 @@ APZCTreeManager::SetKeyboardMap(const Ke
   mKeyboardMap = aKeyboardMap;
 }
 
 void
 APZCTreeManager::ZoomToRect(const ScrollableLayerGuid& aGuid,
                             const CSSRect& aRect,
                             const uint32_t aFlags)
 {
+  // We could probably move this to run on the sampler thread if needed, but
+  // either way we should restrict it to a single thread. For now let's use the
+  // controller thread.
+  APZThreadUtils::AssertOnControllerThread();
+
   RefPtr<AsyncPanZoomController> apzc = GetTargetAPZC(aGuid);
   if (apzc) {
     apzc->ZoomToRect(aRect, aFlags);
   }
 }
 
 void
 APZCTreeManager::ContentReceivedInputBlock(uint64_t aInputBlockId, bool aPreventDefault)

--- a/gfx/layers/apz/util/ChromeProcessController.cpp
+++ b/gfx/layers/apz/util/ChromeProcessController.cpp
@@ -7,16 +7,17 @@
 #include "ChromeProcessController.h"
 
 #include "MainThreadUtils.h"    // for NS_IsMainThread()
 #include "base/message_loop.h"  // for MessageLoop
 #include "mozilla/dom/Element.h"
 #include "mozilla/layers/CompositorBridgeParent.h"
 #include "mozilla/layers/APZCCallbackHelper.h"
 #include "mozilla/layers/APZEventState.h"
+#include "mozilla/layers/APZThreadUtils.h"
 #include "mozilla/layers/IAPZCTreeManager.h"
 #include "mozilla/layers/DoubleTapToZoom.h"
 #include "nsIDocument.h"
 #include "nsIInterfaceRequestorUtils.h"
 #include "nsIPresShell.h"
 #include "nsLayoutUtils.h"
 #include "nsView.h"
 
@@ -153,18 +154,24 @@ ChromeProcessController::HandleDoubleTap
   const float resolution = presShell->ScaleToResolution() ? presShell->GetResolution () : 1.0f;
   CSSPoint point(aPoint.x / resolution, aPoint.y / resolution);
   CSSRect zoomToRect = CalculateRectToZoomTo(document, point);
 
   uint32_t presShellId;
   FrameMetrics::ViewID viewId;
   if (APZCCallbackHelper::GetOrCreateScrollIdentifiers(
       document->GetDocumentElement(), &presShellId, &viewId)) {
-    mAPZCTreeManager->ZoomToRect(
-      ScrollableLayerGuid(aGuid.mLayersId, presShellId, viewId), zoomToRect);
+    APZThreadUtils::RunOnControllerThread(
+      NewRunnableMethod<ScrollableLayerGuid, CSSRect, uint32_t>(
+        "IAPZCTreeManager::ZoomToRect",
+        mAPZCTreeManager,
+        &IAPZCTreeManager::ZoomToRect,
+        ScrollableLayerGuid(aGuid.mLayersId, presShellId, viewId),
+        zoomToRect,
+        ZoomToRectBehavior::DEFAULT_BEHAVIOR));
   }
 }
 
 void
 ChromeProcessController::HandleTap(TapType aType,
                                    const mozilla::LayoutDevicePoint& aPoint,
                                    Modifiers aModifiers,
                                    const ScrollableLayerGuid& aGuid,

--- a/gfx/layers/ipc/APZCTreeManagerParent.cpp
+++ b/gfx/layers/ipc/APZCTreeManagerParent.cpp
@@ -182,17 +182,22 @@ APZCTreeManagerParent::RecvZoomToRect(
     const uint32_t& aFlags)
 {
   if (aGuid.mLayersId != mLayersId) {
     // Guard against bad data from hijacked child processes
     NS_ERROR("Unexpected layers id in RecvZoomToRect; dropping message...");
     return IPC_FAIL_NO_REASON(this);
   }
 
-  mTreeManager->ZoomToRect(aGuid, aRect, aFlags);
+  APZThreadUtils::RunOnControllerThread(
+    NewRunnableMethod<ScrollableLayerGuid, CSSRect, uint32_t>(
+      "layers::IAPZCTreeManager::ZoomToRect",
+      mTreeManager,
+      &IAPZCTreeManager::ZoomToRect,
+      aGuid, aRect, aFlags));
   return IPC_OK();
 }
 
 mozilla::ipc::IPCResult
 APZCTreeManagerParent::RecvContentReceivedInputBlock(
     const uint64_t& aInputBlockId,
     const bool& aPreventDefault)
 {

--- a/widget/nsBaseWidget.cpp
+++ b/widget/nsBaseWidget.cpp
@@ -1928,17 +1928,24 @@ nsBaseWidget::ZoomToRect(const uint32_t&
                          const FrameMetrics::ViewID& aViewId,
                          const CSSRect& aRect,
                          const uint32_t& aFlags)
 {
   if (!mCompositorSession || !mAPZC) {
     return;
   }
   uint64_t layerId = mCompositorSession->RootLayerTreeId();
-  mAPZC->ZoomToRect(ScrollableLayerGuid(layerId, aPresShellId, aViewId), aRect, aFlags);
+  APZThreadUtils::RunOnControllerThread(
+    NewRunnableMethod<ScrollableLayerGuid, CSSRect, uint32_t>(
+      "layers::IAPZCTreeManager::ZoomToRect",
+      mAPZC,
+      &IAPZCTreeManager::ZoomToRect,
+      ScrollableLayerGuid(layerId, aPresShellId, aViewId),
+      aRect,
+      aFlags));
 }
 
 #ifdef ACCESSIBILITY
 
 a11y::Accessible*
 nsBaseWidget::GetRootAccessible()
 {
   NS_ENSURE_TRUE(mWidgetListener, nullptr);