diff --git a/gfx/layers/apz/test/gtest/InputUtils.h b/gfx/layers/apz/test/gtest/InputUtils.h
index 70a0db8be7c8..50757ac218fd 100644
--- a/gfx/layers/apz/test/gtest/InputUtils.h
+++ b/gfx/layers/apz/test/gtest/InputUtils.h
@@ -129,10 +129,6 @@ APZEventResult PanGesture(PanGestureInput::PanGestureType aType,
                           Modifiers aModifiers = MODIFIER_NONE) {
   PanGestureInput input(aType, MillisecondsSinceStartup(aTime), aTime, aPoint,
                         aDelta, aModifiers);
-  if (aType == PanGestureInput::PANGESTURE_END) {
-    input.mFollowedByMomentum = true;
-  }
-
   return aTarget->ReceiveInputEvent(input);
 }
 
diff --git a/widget/InputData.cpp b/widget/InputData.cpp
index 735ce2d62158..d6dfb03c05bc 100644
--- a/widget/InputData.cpp
+++ b/widget/InputData.cpp
@@ -433,7 +433,6 @@ PanGestureInput::PanGestureInput()
       mUserDeltaMultiplierX(1.0),
       mUserDeltaMultiplierY(1.0),
       mHandledByAPZ(false),
-      mFollowedByMomentum(false),
       mRequiresContentResponseIfCannotScrollHorizontallyInStartDirection(false),
       mOverscrollBehaviorAllowsSwipe(false),
       mSimulateMomentum(false),
@@ -453,7 +452,6 @@ PanGestureInput::PanGestureInput(PanGestureType aType, uint32_t aTime,
       mUserDeltaMultiplierX(1.0),
       mUserDeltaMultiplierY(1.0),
       mHandledByAPZ(false),
-      mFollowedByMomentum(false),
       mRequiresContentResponseIfCannotScrollHorizontallyInStartDirection(false),
       mOverscrollBehaviorAllowsSwipe(false),
       mSimulateMomentum(false),
diff --git a/widget/InputData.h b/widget/InputData.h
index afa916ce55c0..e967336304a3 100644
--- a/widget/InputData.h
+++ b/widget/InputData.h
@@ -437,10 +437,6 @@ class PanGestureInput : public InputData {
 
   bool mHandledByAPZ : 1;
 
-  // true if this is a PANGESTURE_END event that will be followed by a
-  // PANGESTURE_MOMENTUMSTART event.
-  bool mFollowedByMomentum : 1;
-
   // If this is true, and this event started a new input block that couldn't
   // find a scrollable target which is scrollable in the horizontal component
   // of the scroll start direction, then this input block needs to be put on
@@ -468,9 +464,6 @@ class PanGestureInput : public InputData {
   bool mIsNoLineOrPageDelta : 1;
 
   void SetHandledByAPZ(bool aHandled) { mHandledByAPZ = aHandled; }
-  void SetFollowedByMomentum(bool aFollowed) {
-    mFollowedByMomentum = aFollowed;
-  }
   void SetRequiresContentResponseIfCannotScrollHorizontallyInStartDirection(
       bool aRequires) {
     mRequiresContentResponseIfCannotScrollHorizontallyInStartDirection =
diff --git a/widget/cocoa/nsChildView.mm b/widget/cocoa/nsChildView.mm
index a38931c43b39..710b604a0890 100644
--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -3247,19 +3247,6 @@ static gfx::IntPoint GetIntegerDeltaForEvent(NSEvent* aEvent) {
       panEvent.SetLineOrPageDeltas(lineOrPageDelta.x, lineOrPageDelta.y);
     }
 
-    if (panEvent.mType == PanGestureInput::PANGESTURE_END) {
-      // Check if there's a momentum start event in the event queue, so that we
-      // can annotate this event.
-      NSEvent* nextWheelEvent = [NSApp nextEventMatchingMask:NSEventMaskScrollWheel
-                                                   untilDate:[NSDate distantPast]
-                                                      inMode:NSDefaultRunLoopMode
-                                                     dequeue:NO];
-      if (nextWheelEvent &&
-          PanGestureTypeForEvent(nextWheelEvent) == PanGestureInput::PANGESTURE_MOMENTUMSTART) {
-        panEvent.mFollowedByMomentum = true;
-      }
-    }
-
     bool canTriggerSwipe = [self shouldConsiderStartingSwipeFromEvent:theEvent] &&
                            SwipeTracker::CanTriggerSwipe(panEvent);
     ;
diff --git a/widget/nsGUIEventIPC.h b/widget/nsGUIEventIPC.h
index e3799bb939d7..66543130b97d 100644
--- a/widget/nsGUIEventIPC.h
+++ b/widget/nsGUIEventIPC.h
@@ -1219,7 +1219,6 @@ struct ParamTraits<mozilla::PanGestureInput>
     WriteParam(aMsg, aParam.mUserDeltaMultiplierY);
     WriteParam(aMsg, aParam.mDeltaType);
     WriteParam(aMsg, aParam.mHandledByAPZ);
-    WriteParam(aMsg, aParam.mFollowedByMomentum);
     WriteParam(
         aMsg,
         aParam
@@ -1244,8 +1243,6 @@ struct ParamTraits<mozilla::PanGestureInput>
            ReadParam(aMsg, aIter, &aResult->mDeltaType) &&
            ReadBoolForBitfield(aMsg, aIter, aResult,
                                &paramType::SetHandledByAPZ) &&
-           ReadBoolForBitfield(aMsg, aIter, aResult,
-                               &paramType::SetFollowedByMomentum) &&
            ReadBoolForBitfield(
                aMsg, aIter, aResult,
                &paramType::