diff --git a/view/public/nsView.h b/view/public/nsView.h
index 91edc51543c..fdcb52a331d 100644
--- a/view/public/nsView.h
+++ b/view/public/nsView.h
@@ -11,6 +11,7 @@
 #include "nsPoint.h"
 #include "nsRegion.h"
 #include "nsCRT.h"
+#include "nsWidgetInitData.h" // for nsWindowType
 #include "nsIWidgetListener.h"
 #include "mozilla/EventForwards.h"
 
diff --git a/widget/nsIWidgetListener.h b/widget/nsIWidgetListener.h
index bafbce35dbc..c5805acb53c 100644
--- a/widget/nsIWidgetListener.h
+++ b/widget/nsIWidgetListener.h
@@ -5,13 +5,15 @@
 #ifndef nsIWidgetListener_h__
 #define nsIWidgetListener_h__
 
-#include "nscore.h"
-#include "nsIXULWindow.h"
-#include "nsRegion.h"
-#include "mozilla/BasicEvents.h"
+#include <stdint.h>
+
+#include "mozilla/EventForwards.h"
 
 class nsView;
+class nsIntRegion;
 class nsIPresShell;
+class nsIWidget;
+class nsIXULWindow;
 
 /**
  * sizemode is an adjunct to widget size
@@ -43,34 +45,35 @@ public:
    * this is likely a listener for a view, which can be determined using
    * GetView. If both methods return null, this will be an nsWebBrowser.
    */
-  virtual nsIXULWindow* GetXULWindow() { return nullptr; }
+  virtual nsIXULWindow* GetXULWindow();
 
   /**
    * If this listener is for an nsView, return it.
    */
-  virtual nsView* GetView() { return nullptr; }
+  virtual nsView* GetView();
 
   /**
    * Return the presshell for this widget listener.
    */
-  virtual nsIPresShell* GetPresShell() { return nullptr; }
+  virtual nsIPresShell* GetPresShell();
 
   /**
    * Called when a window is moved to location (x, y). Returns true if the
    * notification was handled. Coordinates are outer window screen coordinates.
    */
-  virtual bool WindowMoved(nsIWidget* aWidget, int32_t aX, int32_t aY) { return false; }
+  virtual bool WindowMoved(nsIWidget* aWidget, int32_t aX, int32_t aY);
 
   /**
    * Called when a window is resized to (width, height). Returns true if the
    * notification was handled. Coordinates are outer window screen coordinates.
    */
-  virtual bool WindowResized(nsIWidget* aWidget, int32_t aWidth, int32_t aHeight) { return false; }
+  virtual bool WindowResized(nsIWidget* aWidget,
+                             int32_t aWidth, int32_t aHeight);
 
   /**
    * Called when the size mode (minimized, maximized, fullscreen) is changed.
    */
-  virtual void SizeModeChanged(nsSizeMode sizeMode) { }
+  virtual void SizeModeChanged(nsSizeMode aSizeMode);
 
   /**
    * Called when the z-order of the window is changed. Returns true if the
@@ -79,36 +82,37 @@ public:
    * window to place below. On return, aActualBelow will be set to the
    * window actually behind. This generally only applies to Windows.
    */
-  virtual bool ZLevelChanged(bool aImmediate, nsWindowZ *aPlacement,
-                             nsIWidget* aRequestBelow, nsIWidget** aActualBelow) { return false; }
+  virtual bool ZLevelChanged(bool aImmediate, nsWindowZ* aPlacement,
+                             nsIWidget* aRequestBelow,
+                             nsIWidget** aActualBelow);
 
   /**
    * Called when the window is activated and focused.
    */
-  virtual void WindowActivated() { }
+  virtual void WindowActivated();
 
   /**
    * Called when the window is deactivated and no longer focused.
    */
-  virtual void WindowDeactivated() { }
+  virtual void WindowDeactivated();
 
   /**
    * Called when the show/hide toolbar button on the Mac titlebar is pressed.
    */
-  virtual void OSToolbarButtonPressed() { }
+  virtual void OSToolbarButtonPressed();
 
   /**
    * Called when a request is made to close the window. Returns true if the
    * notification was handled. Returns true if the notification was handled.
    */
-  virtual bool RequestWindowClose(nsIWidget* aWidget) { return false; }
+  virtual bool RequestWindowClose(nsIWidget* aWidget);
 
   /*
    * Indicate that a paint is about to occur on this window. This is called
    * at a time when it's OK to change the geometry of this widget or of
    * other widgets. Must be called before every call to PaintWindow.
    */
-  virtual void WillPaintWindow(nsIWidget* aWidget) { }
+  virtual void WillPaintWindow(nsIWidget* aWidget);
 
   /**
    * Paint the specified region of the window. Returns true if the
@@ -116,7 +120,7 @@ public:
    * This is called at a time when it is not OK to change the geometry of
    * this widget or of other widgets.
    */
-  virtual bool PaintWindow(nsIWidget* aWidget, nsIntRegion aRegion) { return false; }
+  virtual bool PaintWindow(nsIWidget* aWidget, nsIntRegion aRegion);
 
   /**
    * Indicates that a paint occurred.
@@ -124,21 +128,18 @@ public:
    * this widget or of other widgets.
    * Must be called after every call to PaintWindow.
    */
-  virtual void DidPaintWindow() { }
+  virtual void DidPaintWindow();
 
   /**
    * Request that layout schedules a repaint on the next refresh driver tick.
    */
-  virtual void RequestRepaint() { }
+  virtual void RequestRepaint();
 
   /**
    * Handle an event.
    */
   virtual nsEventStatus HandleEvent(mozilla::WidgetGUIEvent* aEvent,
-                                    bool aUseAttachedEvents)
-  {
-    return nsEventStatus_eIgnore;
-  }
+                                    bool aUseAttachedEvents);
 };
 
 #endif
diff --git a/widget/xpwidgets/moz.build b/widget/xpwidgets/moz.build
index 287fac0f460..ec3da93c0bb 100644
--- a/widget/xpwidgets/moz.build
+++ b/widget/xpwidgets/moz.build
@@ -29,6 +29,7 @@ CPP_SOURCES += [
     'nsFilePickerProxy.cpp',
     'nsHTMLFormatConverter.cpp',
     'nsIdleService.cpp',
+    'nsIWidgetListener.cpp',
     'nsPrimitiveHelpers.cpp',
     'nsPrintOptionsImpl.cpp',
     'nsPrintSession.cpp',
diff --git a/widget/xpwidgets/nsIWidgetListener.cpp b/widget/xpwidgets/nsIWidgetListener.cpp
new file mode 100644
index 00000000000..a1ad325fc8e
--- /dev/null
+++ b/widget/xpwidgets/nsIWidgetListener.cpp
@@ -0,0 +1,114 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 "nsIWidgetListener.h"
+
+#include "nsRegion.h"
+#include "nsView.h"
+#include "nsIPresShell.h"
+#include "nsIWidget.h"
+#include "nsIXULWindow.h"
+
+#include "mozilla/BasicEvents.h"
+
+using namespace mozilla;
+
+nsIXULWindow*
+nsIWidgetListener::GetXULWindow()
+{
+  return nullptr;
+}
+
+nsView*
+nsIWidgetListener::GetView()
+{
+  return nullptr;
+}
+
+nsIPresShell*
+nsIWidgetListener::GetPresShell()
+{
+  return nullptr;
+}
+
+bool
+nsIWidgetListener::WindowMoved(nsIWidget* aWidget,
+                               int32_t aX,
+                               int32_t aY)
+{
+  return false;
+}
+
+bool
+nsIWidgetListener::WindowResized(nsIWidget* aWidget,
+                                 int32_t aWidth,
+                                 int32_t aHeight)
+{
+  return false;
+}
+
+void
+nsIWidgetListener::SizeModeChanged(nsSizeMode aSizeMode)
+{
+}
+
+bool
+nsIWidgetListener::ZLevelChanged(bool aImmediate,
+                                 nsWindowZ* aPlacement,
+                                 nsIWidget* aRequestBelow,
+                                 nsIWidget** aActualBelow)
+{
+  return false;
+}
+
+void
+nsIWidgetListener::WindowActivated()
+{
+}
+
+void
+nsIWidgetListener::WindowDeactivated()
+{
+}
+
+void
+nsIWidgetListener::OSToolbarButtonPressed()
+{
+}
+
+bool
+nsIWidgetListener::RequestWindowClose(nsIWidget* aWidget)
+{
+  return false;
+}
+
+void
+nsIWidgetListener::WillPaintWindow(nsIWidget* aWidget)
+{
+}
+
+bool
+nsIWidgetListener::PaintWindow(nsIWidget* aWidget,
+                               nsIntRegion aRegion)
+{
+  return false;
+}
+
+void
+nsIWidgetListener::DidPaintWindow()
+{
+}
+
+void
+nsIWidgetListener::RequestRepaint()
+{
+}
+
+nsEventStatus
+nsIWidgetListener::HandleEvent(WidgetGUIEvent* aEvent,
+                               bool aUseAttachedEvents)
+{
+  return nsEventStatus_eIgnore;
+}
diff --git a/xpfe/appshell/src/nsAppShellService.cpp b/xpfe/appshell/src/nsAppShellService.cpp
index 9b65479a810..c7ca8ee1644 100644
--- a/xpfe/appshell/src/nsAppShellService.cpp
+++ b/xpfe/appshell/src/nsAppShellService.cpp
@@ -23,7 +23,9 @@
 #include "nsCRT.h"
 #include "prprf.h"
 
+#include "nsWidgetInitData.h"
 #include "nsWidgetsCID.h"
+#include "nsIWidget.h"
 #include "nsIRequestObserver.h"
 
 /* For implementing GetHiddenWindowAndJSContext */
diff --git a/xpfe/appshell/src/nsChromeTreeOwner.cpp b/xpfe/appshell/src/nsChromeTreeOwner.cpp
index c5dabe5d875..83002cfd79a 100644
--- a/xpfe/appshell/src/nsChromeTreeOwner.cpp
+++ b/xpfe/appshell/src/nsChromeTreeOwner.cpp
@@ -19,6 +19,7 @@
 #include "nsIAuthPrompt.h"
 #include "nsIBrowserDOMWindow.h"
 #include "nsIWebProgress.h"
+#include "nsIWidget.h"
 #include "nsIWindowMediator.h"
 #include "nsIDOMChromeWindow.h"
 #include "nsIDOMNode.h"
diff --git a/xpfe/appshell/src/nsContentTreeOwner.cpp b/xpfe/appshell/src/nsContentTreeOwner.cpp
index e55604fcc61..7e28e3c5c2a 100644
--- a/xpfe/appshell/src/nsContentTreeOwner.cpp
+++ b/xpfe/appshell/src/nsContentTreeOwner.cpp
@@ -34,6 +34,7 @@
 #include "nsDocShellCID.h"
 #include "nsIExternalURLHandlerService.h"
 #include "nsIMIMEInfo.h"
+#include "nsIWidget.h"
 #include "mozilla/BrowserElementParent.h"
 
 #include "nsIDOMDocument.h"
diff --git a/xpfe/appshell/src/nsWebShellWindow.cpp b/xpfe/appshell/src/nsWebShellWindow.cpp
index 89b88762477..4e7132042bf 100644
--- a/xpfe/appshell/src/nsWebShellWindow.cpp
+++ b/xpfe/appshell/src/nsWebShellWindow.cpp
@@ -26,6 +26,7 @@
 
 #include "nsIDOMXULElement.h"
 
+#include "nsWidgetInitData.h"
 #include "nsWidgetsCID.h"
 #include "nsIWidget.h"
 #include "nsIWidgetListener.h"
diff --git a/xpfe/appshell/src/nsWebShellWindow.h b/xpfe/appshell/src/nsWebShellWindow.h
index 89f0fc9eacb..88281bb96ba 100644
--- a/xpfe/appshell/src/nsWebShellWindow.h
+++ b/xpfe/appshell/src/nsWebShellWindow.h
@@ -16,6 +16,8 @@
 /* Forward declarations.... */
 class nsIURI;
 
+struct nsWidgetInitData;
+
 namespace mozilla {
 class WebShellWindowTimerCallback;
 } // namespace mozilla
diff --git a/xpfe/appshell/src/nsXULWindow.h b/xpfe/appshell/src/nsXULWindow.h
index cd1f4d978c0..3fc09dec556 100644
--- a/xpfe/appshell/src/nsXULWindow.h
+++ b/xpfe/appshell/src/nsXULWindow.h
@@ -17,6 +17,7 @@
 #include "nsString.h"
 #include "nsWeakReference.h"
 #include "nsCOMArray.h"
+#include "nsRect.h"
 
 // Interfaces needed
 #include "nsIBaseWindow.h"