--- a/dom/events/EventStateManager.cpp
+++ b/dom/events/EventStateManager.cpp
@@ -662,17 +662,17 @@ EventStateManager::PreHandleEvent(nsPres
 
     // Flag helps to suppress double event sending into process of content.
     // For more information see comment above, at eMouseEnterIntoWidget case.
     aEvent->StopCrossProcessForwarding();
 
     // If the event is not a top-level window exit, then it's not
     // really an exit --- we may have traversed widget boundaries but
     // we're still in our toplevel window.
-    if (mouseEvent->exit != WidgetMouseEvent::eTopLevel) {
+    if (mouseEvent->mExitFrom != WidgetMouseEvent::eTopLevel) {
       // Treat it as a synthetic move so we don't generate spurious
       // "exit" or "move" events.  Any necessary "out" or "over" events
       // will be generated by GenerateMouseEnterExit
       mouseEvent->mMessage = eMouseMove;
       mouseEvent->mReason = WidgetMouseEvent::eSynthesized;
       // then fall through...
     } else {
       if (sPointerEventEnabled) {
@@ -3938,17 +3938,17 @@ EventStateManager::DispatchMouseOrPointe
     // If we are entering/leaving remote content, dispatch a mouse enter/exit
     // event to the remote frame.
     if (IsRemoteTarget(aTargetContent)) {
       if (aMessage == eMouseOut) {
         // For remote content, send a "top-level" widget mouse exit event.
         nsAutoPtr<WidgetMouseEvent> remoteEvent;
         CreateMouseOrPointerWidgetEvent(aMouseEvent, eMouseExitFromWidget,
                                         aRelatedContent, remoteEvent);
-        remoteEvent->exit = WidgetMouseEvent::eTopLevel;
+        remoteEvent->mExitFrom = WidgetMouseEvent::eTopLevel;
 
         // mCurrentTarget is set to the new target, so we must reset it to the
         // old target and then dispatch a cross-process event. (mCurrentTarget
         // will be set back below.) HandleCrossProcessEvent will query for the
         // proper target via GetEventTarget which will return mCurrentTarget.
         mCurrentTarget = targetFrame;
         HandleCrossProcessEvent(remoteEvent, &status);
       } else if (aMessage == eMouseOver) {

--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -7561,17 +7561,17 @@ PresShell::HandleEvent(nsIFrame* aFrame,
 
     // all touch events except for touchstart use a captured target
     if (aEvent->mClass == eTouchEventClass && aEvent->mMessage != eTouchStart) {
       captureRetarget = true;
     }
 
     WidgetMouseEvent* mouseEvent = aEvent->AsMouseEvent();
     bool isWindowLevelMouseExit = (aEvent->mMessage == eMouseExitFromWidget) &&
-      (mouseEvent && mouseEvent->exit == WidgetMouseEvent::eTopLevel);
+      (mouseEvent && mouseEvent->mExitFrom == WidgetMouseEvent::eTopLevel);
 
     // Get the frame at the event point. However, don't do this if we're
     // capturing and retargeting the event because the captured frame will
     // be used instead below. Also keep using the root frame if we're dealing
     // with a window-level mouse exit event since we want to start sending
     // mouse out events at the root EventStateManager.
     if (!captureRetarget && !isWindowLevelMouseExit) {
       nsPoint eventPoint;

--- a/widget/MouseEvents.h
+++ b/widget/MouseEvents.h
@@ -201,29 +201,29 @@ public:
     eChild,
     eTopLevel
   };
 
 protected:
   WidgetMouseEvent()
     : mReason(eReal)
     , mContextMenuTrigger(eNormal)
-    , exit(eChild)
+    , mExitFrom(eChild)
     , acceptActivation(false)
     , ignoreRootScrollFrame(false)
     , clickCount(0)
   {
   }
 
   WidgetMouseEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget,
                    EventClassID aEventClassID, Reason aReason)
     : WidgetMouseEventBase(aIsTrusted, aMessage, aWidget, aEventClassID)
     , mReason(aReason)
     , mContextMenuTrigger(eNormal)
-    , exit(eChild)
+    , mExitFrom(eChild)
     , acceptActivation(false)
     , ignoreRootScrollFrame(false)
     , clickCount(0)
   {
   }
 
 public:
   virtual WidgetMouseEvent* AsMouseEvent() override { return this; }
@@ -231,17 +231,17 @@ public:
   WidgetMouseEvent(bool aIsTrusted,
                    EventMessage aMessage,
                    nsIWidget* aWidget,
                    Reason aReason,
                    ContextMenuTrigger aContextMenuTrigger = eNormal)
     : WidgetMouseEventBase(aIsTrusted, aMessage, aWidget, eMouseEventClass)
     , mReason(aReason)
     , mContextMenuTrigger(aContextMenuTrigger)
-    , exit(eChild)
+    , mExitFrom(eChild)
     , acceptActivation(false)
     , ignoreRootScrollFrame(false)
     , clickCount(0)
   {
     if (aMessage == eContextMenu) {
       button = (mContextMenuTrigger == eNormal) ? eRightButton : eLeftButton;
     }
   }
@@ -269,17 +269,17 @@ public:
     result->mFlags = mFlags;
     return result;
   }
 
   Reason mReason;
 
   ContextMenuTrigger mContextMenuTrigger;
 
-  ExitFrom exit;
+  ExitFrom mExitFrom;
 
   // Special return code for MOUSE_ACTIVATE to signal.
   // If the target accepts activation (1), or denies it (0).
   bool acceptActivation;
   // Whether the event should ignore scroll frame bounds during dispatch.
   bool ignoreRootScrollFrame;
 
   /// The number of mouse clicks.

--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -4597,17 +4597,17 @@ NSEvent* gLastDragMouseDownEvent = nil;
 
   NSPoint windowEventLocation = nsCocoaUtils::EventLocationForWindow(aEvent, [self window]);
   NSPoint localEventLocation = [self convertPoint:windowEventLocation fromView:nil];
 
   EventMessage msg = aEnter ? eMouseEnterIntoWidget : eMouseExitFromWidget;
   WidgetMouseEvent event(true, msg, mGeckoChild, WidgetMouseEvent::eReal);
   event.mRefPoint = mGeckoChild->CocoaPointsToDevPixels(localEventLocation);
 
-  event.exit = aExitFrom;
+  event.mExitFrom = aExitFrom;
 
   nsEventStatus status; // ignored
   mGeckoChild->DispatchEvent(&event, status);
 }
 
 - (void)updateWindowDraggableState
 {
   // Trigger update to the window server.
@@ -6328,17 +6328,17 @@ ChildViewMouseTracker::ReEvaluateMouseEn
     // Send enter and / or exit events.
     WidgetMouseEvent::ExitFrom exitFrom =
       [sLastMouseEventView window] == [oldView window] ?
         WidgetMouseEvent::eChild : WidgetMouseEvent::eTopLevel;
     [oldView sendMouseEnterOrExitEvent:aEvent
                                  enter:NO
                               exitFrom:exitFrom];
     // After the cursor exits the window set it to a visible regular arrow cursor.
-    if (type == WidgetMouseEvent::eTopLevel) {
+    if (exitFrom == WidgetMouseEvent::eTopLevel) {
       [[nsCursorManager sharedInstance] setCursor:eCursor_standard];
     }
     [sLastMouseEventView sendMouseEnterOrExitEvent:aEvent
                                              enter:YES
                                           exitFrom:exitFrom];
   }
 }
 

--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -2570,17 +2570,17 @@ nsWindow::OnLeaveNotifyEvent(GdkEventCro
         return;
 
     WidgetMouseEvent event(true, eMouseExitFromWidget, this,
                            WidgetMouseEvent::eReal);
 
     event.mRefPoint = GdkEventCoordsToDevicePixels(aEvent->x, aEvent->y);
     event.AssignEventTime(GetWidgetEventTime(aEvent->time));
 
-    event.exit = is_top_level_mouse_exit(mGdkWindow, aEvent)
+    event.mExitFrom = is_top_level_mouse_exit(mGdkWindow, aEvent)
         ? WidgetMouseEvent::eTopLevel : WidgetMouseEvent::eChild;
 
     LOG(("OnLeaveNotify: %p\n", (void *)this));
 
     DispatchInputEvent(&event);
 }
 
 template <typename Event> static LayoutDeviceIntPoint

--- a/widget/nsGUIEventIPC.h
+++ b/widget/nsGUIEventIPC.h
@@ -229,17 +229,17 @@ struct ParamTraits<mozilla::WidgetMouseE
 
   static void Write(Message* aMsg, const paramType& aParam)
   {
     WriteParam(aMsg, static_cast<mozilla::WidgetMouseEventBase>(aParam));
     WriteParam(aMsg, aParam.ignoreRootScrollFrame);
     WriteParam(aMsg, static_cast<paramType::ReasonType>(aParam.mReason));
     WriteParam(aMsg, static_cast<paramType::ContextMenuTriggerType>(
                        aParam.mContextMenuTrigger));
-    WriteParam(aMsg, static_cast<paramType::ExitFromType>(aParam.exit));
+    WriteParam(aMsg, static_cast<paramType::ExitFromType>(aParam.mExitFrom));
     WriteParam(aMsg, aParam.clickCount);
   }
 
   static bool Read(const Message* aMsg, void** aIter, paramType* aResult)
   {
     bool rv;
     paramType::ReasonType reason = 0;
     paramType::ContextMenuTriggerType contextMenuTrigger = 0;
@@ -249,17 +249,17 @@ struct ParamTraits<mozilla::WidgetMouseE
          ReadParam(aMsg, aIter, &aResult->ignoreRootScrollFrame) &&
          ReadParam(aMsg, aIter, &reason) &&
          ReadParam(aMsg, aIter, &contextMenuTrigger) &&
          ReadParam(aMsg, aIter, &exitFrom) &&
          ReadParam(aMsg, aIter, &aResult->clickCount);
     aResult->mReason = static_cast<paramType::Reason>(reason);
     aResult->mContextMenuTrigger =
       static_cast<paramType::ContextMenuTrigger>(contextMenuTrigger);
-    aResult->exit = static_cast<paramType::ExitFrom>(exitFrom);
+    aResult->mExitFrom = static_cast<paramType::ExitFrom>(exitFrom);
     return rv;
   }
 };
 
 
 template<>
 struct ParamTraits<mozilla::WidgetDragEvent>
 {

--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -4094,18 +4094,19 @@ nsWindow::DispatchMouseEvent(EventMessag
       sLastMouseDownTime = curMsgTime;
       break;
     case eMouseMove:
       if (!insideMovementThreshold) {
         sLastClickCount = 0;
       }
       break;
     case eMouseExitFromWidget:
-      event.exit = IsTopLevelMouseExit(mWnd) ?
-                     WidgetMouseEvent::eTopLevel : WidgetMouseEvent::eChild;
+      event.mExitFrom =
+        IsTopLevelMouseExit(mWnd) ? WidgetMouseEvent::eTopLevel :
+                                    WidgetMouseEvent::eChild;
       break;
     default:
       break;
   }
   event.clickCount = sLastClickCount;
 
 #ifdef NS_DEBUG_XX
   MOZ_LOG(gWindowsLog, LogLevel::Info,