--- a/dom/events/EventStateManager.cpp
+++ b/dom/events/EventStateManager.cpp
@@ -3171,17 +3171,17 @@ EventStateManager::PostHandleEvent(nsPre
       nsPluginFrame* pluginFrame = do_QueryFrame(frameToScroll);
 
       // When APZ is enabled, the actual scroll animation might be handled by
       // the compositor.
       WheelPrefs::Action action;
       if (pluginFrame) {
         MOZ_ASSERT(pluginFrame->WantsToHandleWheelEventAsDefaultAction());
         action = WheelPrefs::ACTION_SEND_TO_PLUGIN;
-      } else if (!wheelEvent->mayHaveMomentum &&
+      } else if (!wheelEvent->mMayHaveMomentum &&
             nsLayoutUtils::IsScrollFrameWithSnapping(frameToScroll)) {
         // If the target has scroll-snapping points then we want to handle
         // the wheel event on the main thread even if we have APZ enabled. Do
         // so and let the APZ know that it should ignore this event. However,
         // if the wheel event is synthesized from a Mac trackpad or other device
         // that can generate additional momentum events, then we should allow
         // APZ to handle it, because it will track the velocity and predicted
         // destination from the momentum.

--- a/widget/InputData.cpp
+++ b/widget/InputData.cpp
@@ -387,17 +387,17 @@ PanGestureInput::ToWidgetWheelEvent(nsIW
   wheelEvent.mModifiers = this->modifiers;
   wheelEvent.mTime = mTime;
   wheelEvent.mTimeStamp = mTimeStamp;
   wheelEvent.refPoint =
     RoundedToInt(ViewAs<LayoutDevicePixel>(mPanStartPoint,
       PixelCastJustification::LayoutDeviceIsScreenForUntransformedEvent));
   wheelEvent.buttons = 0;
   wheelEvent.mDeltaMode = nsIDOMWheelEvent::DOM_DELTA_PIXEL;
-  wheelEvent.mayHaveMomentum = true; // pan inputs may have momentum
+  wheelEvent.mMayHaveMomentum = true; // pan inputs may have momentum
   wheelEvent.isMomentum = IsMomentum();
   wheelEvent.lineOrPageDeltaX = mLineOrPageDeltaX;
   wheelEvent.lineOrPageDeltaY = mLineOrPageDeltaY;
   wheelEvent.mDeltaX = mPanDisplacement.x;
   wheelEvent.mDeltaY = mPanDisplacement.y;
   wheelEvent.mFlags.mHandledByAPZ = mHandledByAPZ;
   return wheelEvent;
 }
@@ -465,17 +465,17 @@ ScrollWheelInput::ScrollWheelInput(const
   , mHandledByAPZ(aWheelEvent.mFlags.mHandledByAPZ)
   , mDeltaX(aWheelEvent.mDeltaX)
   , mDeltaY(aWheelEvent.mDeltaY)
   , mLineOrPageDeltaX(aWheelEvent.lineOrPageDeltaX)
   , mLineOrPageDeltaY(aWheelEvent.lineOrPageDeltaY)
   , mScrollSeriesNumber(0)
   , mUserDeltaMultiplierX(1.0)
   , mUserDeltaMultiplierY(1.0)
-  , mMayHaveMomentum(aWheelEvent.mayHaveMomentum)
+  , mMayHaveMomentum(aWheelEvent.mMayHaveMomentum)
   , mIsMomentum(aWheelEvent.isMomentum)
   , mAllowToOverrideSystemScrollSpeed(
       aWheelEvent.mAllowToOverrideSystemScrollSpeed)
 {
   mOrigin =
     ScreenPoint(ViewAs<ScreenPixel>(aWheelEvent.refPoint,
       PixelCastJustification::LayoutDeviceIsScreenForUntransformedEvent));
 }
@@ -487,17 +487,17 @@ ScrollWheelInput::ToWidgetWheelEvent(nsI
   wheelEvent.mModifiers = this->modifiers;
   wheelEvent.mTime = mTime;
   wheelEvent.mTimeStamp = mTimeStamp;
   wheelEvent.refPoint =
     RoundedToInt(ViewAs<LayoutDevicePixel>(mOrigin,
       PixelCastJustification::LayoutDeviceIsScreenForUntransformedEvent));
   wheelEvent.buttons = 0;
   wheelEvent.mDeltaMode = DeltaModeForDeltaType(mDeltaType);
-  wheelEvent.mayHaveMomentum = mMayHaveMomentum;
+  wheelEvent.mMayHaveMomentum = mMayHaveMomentum;
   wheelEvent.isMomentum = mIsMomentum;
   wheelEvent.mDeltaX = mDeltaX;
   wheelEvent.mDeltaY = mDeltaY;
   wheelEvent.lineOrPageDeltaX = mLineOrPageDeltaX;
   wheelEvent.lineOrPageDeltaY = mLineOrPageDeltaY;
   wheelEvent.mAllowToOverrideSystemScrollSpeed =
     mAllowToOverrideSystemScrollSpeed;
   wheelEvent.mFlags.mHandledByAPZ = mHandledByAPZ;

--- a/widget/MouseEvents.h
+++ b/widget/MouseEvents.h
@@ -471,17 +471,17 @@ public:
 
   WidgetWheelEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget)
     : WidgetMouseEventBase(aIsTrusted, aMessage, aWidget, eWheelEventClass)
     , mDeltaX(0.0)
     , mDeltaY(0.0)
     , mDeltaZ(0.0)
     , mDeltaMode(nsIDOMWheelEvent::DOM_DELTA_PIXEL)
     , mCustomizedByUserPrefs(false)
-    , mayHaveMomentum(false)
+    , mMayHaveMomentum(false)
     , isMomentum(false)
     , mIsNoLineOrPageDelta(false)
     , lineOrPageDeltaX(0)
     , lineOrPageDeltaY(0)
     , scrollType(SCROLL_DEFAULT)
     , overflowDeltaX(0.0)
     , overflowDeltaY(0.0)
     , mViewPortIsOverscrolled(false)
@@ -524,17 +524,17 @@ public:
 
   // Following members are for internal use only, not for DOM event.
 
   // If the delta values are computed from prefs, this value is true.
   // Otherwise, i.e., they are computed from native events, false.
   bool mCustomizedByUserPrefs;
 
   // true if the momentum events directly tied to this event may follow it.
-  bool mayHaveMomentum;
+  bool mMayHaveMomentum;
   // true if the event is caused by momentum.
   bool isMomentum;
 
   // If device event handlers don't know when they should set lineOrPageDeltaX
   // and lineOrPageDeltaY, this is true.  Otherwise, false.
   // If mIsNoLineOrPageDelta is true, ESM will generate
   // eLegacyMouseLineOrPageScroll events when accumulated delta values reach
   // a line height.
@@ -610,17 +610,17 @@ public:
   {
     AssignMouseEventBaseData(aEvent, aCopyTargets);
 
     mDeltaX = aEvent.mDeltaX;
     mDeltaY = aEvent.mDeltaY;
     mDeltaZ = aEvent.mDeltaZ;
     mDeltaMode = aEvent.mDeltaMode;
     mCustomizedByUserPrefs = aEvent.mCustomizedByUserPrefs;
-    mayHaveMomentum = aEvent.mayHaveMomentum;
+    mMayHaveMomentum = aEvent.mMayHaveMomentum;
     isMomentum = aEvent.isMomentum;
     mIsNoLineOrPageDelta = aEvent.mIsNoLineOrPageDelta;
     lineOrPageDeltaX = aEvent.lineOrPageDeltaX;
     lineOrPageDeltaY = aEvent.lineOrPageDeltaY;
     scrollType = aEvent.scrollType;
     overflowDeltaX = aEvent.overflowDeltaX;
     overflowDeltaY = aEvent.overflowDeltaY;
     mViewPortIsOverscrolled = aEvent.mViewPortIsOverscrolled;

--- a/widget/nsGUIEventIPC.h
+++ b/widget/nsGUIEventIPC.h
@@ -160,17 +160,17 @@ struct ParamTraits<mozilla::WidgetWheelE
   static void Write(Message* aMsg, const paramType& aParam)
   {
     WriteParam(aMsg, static_cast<mozilla::WidgetMouseEventBase>(aParam));
     WriteParam(aMsg, aParam.mDeltaX);
     WriteParam(aMsg, aParam.mDeltaY);
     WriteParam(aMsg, aParam.mDeltaZ);
     WriteParam(aMsg, aParam.mDeltaMode);
     WriteParam(aMsg, aParam.mCustomizedByUserPrefs);
-    WriteParam(aMsg, aParam.mayHaveMomentum);
+    WriteParam(aMsg, aParam.mMayHaveMomentum);
     WriteParam(aMsg, aParam.isMomentum);
     WriteParam(aMsg, aParam.mIsNoLineOrPageDelta);
     WriteParam(aMsg, aParam.lineOrPageDeltaX);
     WriteParam(aMsg, aParam.lineOrPageDeltaY);
     WriteParam(aMsg, static_cast<int32_t>(aParam.scrollType));
     WriteParam(aMsg, aParam.overflowDeltaX);
     WriteParam(aMsg, aParam.overflowDeltaY);
     WriteParam(aMsg, aParam.mViewPortIsOverscrolled);
@@ -184,17 +184,17 @@ struct ParamTraits<mozilla::WidgetWheelE
     bool rv =
       ReadParam(aMsg, aIter,
                 static_cast<mozilla::WidgetMouseEventBase*>(aResult)) &&
       ReadParam(aMsg, aIter, &aResult->mDeltaX) &&
       ReadParam(aMsg, aIter, &aResult->mDeltaY) &&
       ReadParam(aMsg, aIter, &aResult->mDeltaZ) &&
       ReadParam(aMsg, aIter, &aResult->mDeltaMode) &&
       ReadParam(aMsg, aIter, &aResult->mCustomizedByUserPrefs) &&
-      ReadParam(aMsg, aIter, &aResult->mayHaveMomentum) &&
+      ReadParam(aMsg, aIter, &aResult->mMayHaveMomentum) &&
       ReadParam(aMsg, aIter, &aResult->isMomentum) &&
       ReadParam(aMsg, aIter, &aResult->mIsNoLineOrPageDelta) &&
       ReadParam(aMsg, aIter, &aResult->lineOrPageDeltaX) &&
       ReadParam(aMsg, aIter, &aResult->lineOrPageDeltaY) &&
       ReadParam(aMsg, aIter, &scrollType) &&
       ReadParam(aMsg, aIter, &aResult->overflowDeltaX) &&
       ReadParam(aMsg, aIter, &aResult->overflowDeltaY) &&
       ReadParam(aMsg, aIter, &aResult->mViewPortIsOverscrolled) &&