--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -68,23 +68,18 @@ using mozilla::DefaultXDisplay;
 #include "nsContentCID.h"
 #include "nsWidgetsCID.h"
 static NS_DEFINE_CID(kWidgetCID, NS_CHILD_CID);
 static NS_DEFINE_CID(kAppShellCID, NS_APPSHELL_CID);
 
 #ifdef XP_WIN
 #include <wtypes.h>
 #include <winuser.h>
-#ifndef WM_MOUSEHWHEEL
-#define WM_MOUSEHWHEEL (0x020E)
-#endif
-#ifndef SPI_GETWHEELSCROLLCHARS
-#define SPI_GETWHEELSCROLLCHARS (0x006C)
-#endif
-#endif
+#include "mozilla/widget/WinMessages.h"
+#endif // #ifdef XP_WIN
 
 #ifdef XP_MACOSX
 #include "ComplexTextInputPanel.h"
 #include "nsIDOMXULDocument.h"
 #include "nsIDOMXULCommandDispatcher.h"
 #endif
 
 #ifdef MOZ_WIDGET_GTK

--- a/dom/plugins/ipc/PluginInstanceChild.cpp
+++ b/dom/plugins/ipc/PluginInstanceChild.cpp
@@ -51,20 +51,21 @@ using namespace std;
 #include <gdk/gdkx.h>
 #include <gdk/gdk.h>
 #include "gtk2xtbin.h"
 
 #elif defined(MOZ_WIDGET_QT)
 #undef KeyPress
 #undef KeyRelease
 #elif defined(OS_WIN)
-#ifndef WM_MOUSEHWHEEL
-#define WM_MOUSEHWHEEL     0x020E
-#endif
-
+
+#include <windows.h>
+#include <windowsx.h>
+
+#include "mozilla/widget/WinMessages.h"
 #include "nsWindowsDllInterceptor.h"
 
 typedef BOOL (WINAPI *User32TrackPopupMenu)(HMENU hMenu,
                                             UINT uFlags,
                                             int x,
                                             int y,
                                             int nReserved,
                                             HWND hWnd,
@@ -89,19 +90,16 @@ static Imm32ImmReleaseContext sImm32ImmR
 static Imm32ImmGetCompositionString sImm32ImmGetCompositionStringStub = nullptr;
 static Imm32ImmSetCandidateWindow sImm32ImmSetCandidateWindowStub = nullptr;
 static Imm32ImmNotifyIME sImm32ImmNotifyIME = nullptr;
 static PluginInstanceChild* sCurrentPluginInstance = nullptr;
 static const HIMC sHookIMC = (const HIMC)0xefefefef;
 
 using mozilla::gfx::SharedDIB;
 
-#include <windows.h>
-#include <windowsx.h>
-
 // Flash WM_USER message delay time for PostDelayedTask. Borrowed
 // from Chromium's web plugin delegate src. See 'flash msg throttling
 // helpers' section for details.
 const int kFlashWMUSERMessageThrottleDelayMs = 5;
 
 static const TCHAR kPluginIgnoreSubclassProperty[] = TEXT("PluginIgnoreSubclassProperty");
 
 #elif defined(XP_MACOSX)

copy from widget/windows/nsWindowDefs.h
copy to widget/windows/WinMessages.h
--- a/widget/windows/nsWindowDefs.h
+++ b/widget/windows/WinMessages.h
@@ -1,32 +1,22 @@
 /* -*- 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/. */
 
-#ifndef WindowDefs_h__
-#define WindowDefs_h__
-
-/*
- * nsWindowDefs - nsWindow related definitions, consts, and macros.
- */
+#ifndef mozilla_widget_WinMessages_h_
+#define mozilla_widget_WinMessages_h_
 
-#include "nsBaseWidget.h"
-#include "nsdefs.h"
-#include "resource.h"
+/*****************************************************************************
+ * MOZ_WM_* messages
+ ****************************************************************************/
 
-/**************************************************************
- *
- * SECTION: defines
- * 
- **************************************************************/
-
-// A magic APP message that can be sent to quit, sort of like a QUERYENDSESSION/ENDSESSION,
-// but without the query.
+// A magic APP message that can be sent to quit, sort of like a
+// QUERYENDSESSION/ENDSESSION, but without the query.
 #define MOZ_WM_APP_QUIT                   (WM_APP+0x0300)
 // Used as a "tracer" event to probe event loop latency.
 #define MOZ_WM_TRACE                      (WM_APP+0x0301)
 // Our internal message for WM_MOUSEWHEEL, WM_MOUSEHWHEEL, WM_VSCROLL and
 // WM_HSCROLL
 #define MOZ_WM_MOUSEVWHEEL                (WM_APP+0x0310)
 #define MOZ_WM_MOUSEHWHEEL                (WM_APP+0x0311)
 #define MOZ_WM_VSCROLL                    (WM_APP+0x0312)
@@ -43,16 +33,26 @@
 #define MOZ_WM_SKEWFIX                    (WM_APP+0x0316)
 // Internal message used for hiding the on-screen keyboard
 #define MOZ_WM_DISMISS_ONSCREEN_KEYBOARD  (WM_APP+0x0317)
 
 // Internal message for ensuring the file picker is visible on multi monitor
 // systems, and when the screen resolution changes.
 #define MOZ_WM_ENSUREVISIBLE              (WM_APP+0x374F)
 
+// XXX Should rename them to MOZ_WM_* and use safer values!
+// Messages for fullscreen transition window
+#define WM_FULLSCREEN_TRANSITION_BEFORE   (WM_USER + 0)
+#define WM_FULLSCREEN_TRANSITION_AFTER    (WM_USER + 1)
+
+/*****************************************************************************
+ * WM_* messages and related constants which may not be defined by
+ * old Windows SDK
+ ****************************************************************************/
+
 #ifndef SM_CXPADDEDBORDER
 #define SM_CXPADDEDBORDER                 92
 #endif
 
 // require WINVER >= 0x601
 #ifndef SM_MAXIMUMTOUCHES
 #define SM_MAXIMUMTOUCHES                 95
 #endif
@@ -105,30 +105,19 @@
 #endif
 #ifndef WM_DWMCOLORIZATIONCOLORCHANGED
 #define WM_DWMCOLORIZATIONCOLORCHANGED    0x0320
 #endif
 #ifndef WM_DWMWINDOWMAXIMIZEDCHANGE
 #define WM_DWMWINDOWMAXIMIZEDCHANGE       0x0321
 #endif
 
-// ConstrainPosition window positioning slop value
-#define kWindowPositionSlop               20
-
-// Origin of the system context menu when displayed in full screen mode
-#define MOZ_SYSCONTEXT_X_POS              20
-#define MOZ_SYSCONTEXT_Y_POS              20
-
 // Drop shadow window style
 #define CS_XP_DROPSHADOW                  0x00020000
 
-// Don't put more than this many rects in the dirty region, just fluff
-// out to the bounding-box if there are more
-#define MAX_RECTS_IN_REGION               100
-
 // App Command messages for IntelliMouse and Natural Keyboard Pro
 // These messages are not included in Visual C++ 6.0, but are in 7.0+
 #ifndef WM_APPCOMMAND
 #define WM_APPCOMMAND                     0x0319
 #endif
 
 #define FAPPCOMMAND_MASK                  0xF000
 
@@ -149,17 +138,17 @@
   #define APPCOMMAND_BROWSER_FAVORITES      6
   #define APPCOMMAND_BROWSER_HOME           7
 
   #define APPCOMMAND_MEDIA_NEXTTRACK        11
   #define APPCOMMAND_MEDIA_PREVIOUSTRACK    12
   #define APPCOMMAND_MEDIA_STOP             13
   #define APPCOMMAND_MEDIA_PLAY_PAUSE       14
 
-  /* 
+  /*
    * Additional commands currently not in use.
    *
    *#define APPCOMMAND_VOLUME_MUTE            8
    *#define APPCOMMAND_VOLUME_DOWN            9
    *#define APPCOMMAND_VOLUME_UP              10
    *#define APPCOMMAND_LAUNCH_MAIL            15
    *#define APPCOMMAND_LAUNCH_MEDIA_SELECT    16
    *#define APPCOMMAND_LAUNCH_APP1            17
@@ -179,117 +168,9 @@
   /*
    *#define GET_DEVICE_LPARAM(lParam)         ((WORD)(HIWORD(lParam) & FAPPCOMMAND_MASK))
    *#define GET_MOUSEORKEY_LPARAM             GET_DEVICE_LPARAM
    *#define GET_FLAGS_LPARAM(lParam)          (LOWORD(lParam))
    *#define GET_KEYSTATE_LPARAM(lParam)       GET_FLAGS_LPARAM(lParam)
    */
 #endif // #ifndef APPCOMMAND_BROWSER_BACKWARD
 
-//Tablet PC Mouse Input Source
-#define TABLET_INK_SIGNATURE 0xFFFFFF00
-#define TABLET_INK_CHECK     0xFF515700
-#define TABLET_INK_TOUCH     0x00000080
-#define MOUSE_INPUT_SOURCE() WinUtils::GetMouseInputSource()
-
-// Messages for fullscreen transition window
-#define WM_FULLSCREEN_TRANSITION_BEFORE     (WM_USER + 0)
-#define WM_FULLSCREEN_TRANSITION_AFTER      (WM_USER + 1)
-
-/**************************************************************
- *
- * SECTION: enums
- * 
- **************************************************************/
-
-// nsWindow::sCanQuit
-typedef enum
-{
-    TRI_UNKNOWN = -1,
-    TRI_FALSE = 0,
-    TRI_TRUE = 1
-} TriStateBool;
-
-/**************************************************************
- *
- * SECTION: constants
- * 
- **************************************************************/
-
-/*
- * Native windows class names
- *
- * ::: IMPORTANT :::
- *
- * External apps and drivers depend on window class names.
- * For example, changing the window classes could break
- * touchpad scrolling or screen readers.
- */
-const uint32_t kMaxClassNameLength   = 40;
-const wchar_t kClassNameHidden[]     = L"MozillaHiddenWindowClass";
-const wchar_t kClassNameGeneral[]    = L"MozillaWindowClass";
-const wchar_t kClassNameDialog[]     = L"MozillaDialogClass";
-const wchar_t kClassNameDropShadow[] = L"MozillaDropShadowWindowClass";
-const wchar_t kClassNameTemp[]       = L"MozillaTempWindowClass";
-const wchar_t kClassNameTransition[] = L"MozillaTransitionWindowClass";
-
-/**************************************************************
- *
- * SECTION: structs
- * 
- **************************************************************/
-
-// Used for synthesizing events
-struct KeyPair {
-  uint8_t mGeneral;
-  uint8_t mSpecific;
-  KeyPair(uint32_t aGeneral, uint32_t aSpecific)
-    : mGeneral(uint8_t(aGeneral)), mSpecific(uint8_t(aSpecific)) {}
-};
-
-#if (WINVER < 0x0600)
-struct TITLEBARINFOEX
-{
-    DWORD cbSize;
-    RECT rcTitleBar;
-    DWORD rgstate[CCHILDREN_TITLEBAR + 1];
-    RECT rgrect[CCHILDREN_TITLEBAR + 1];
-};
-#endif
-
-namespace mozilla {
-namespace widget {
-
-struct MSGResult
-{
-  // Result for the message.
-  LRESULT& mResult;
-  // If mConsumed is true, the caller shouldn't call next wndproc.
-  bool mConsumed;
-
-  MSGResult(LRESULT* aResult = nullptr) :
-    mResult(aResult ? *aResult : mDefaultResult), mConsumed(false)
-  {
-  }
-
-private:
-  LRESULT mDefaultResult;
-};
-
-} // namespace widget
-} // namespace mozilla
-
-/**************************************************************
- *
- * SECTION: macros
- * 
- **************************************************************/
-
-#define NSRGB_2_COLOREF(color) \
-      RGB(NS_GET_R(color),NS_GET_G(color),NS_GET_B(color))
-#define COLOREF_2_NSRGB(color) \
-      NS_RGB(GetRValue(color), GetGValue(color), GetBValue(color))
-
-#define VERIFY_WINDOW_STYLE(s) \
-      NS_ASSERTION(((s) & (WS_CHILD | WS_POPUP)) != (WS_CHILD | WS_POPUP), \
-      "WS_POPUP and WS_CHILD are mutually exclusive")
-
-#endif /* WindowDefs_h__ */
+#endif // #ifndef mozilla_widget_WinMessages_h_

--- a/widget/windows/moz.build
+++ b/widget/windows/moz.build
@@ -9,16 +9,17 @@ TEST_DIRS += ['tests']
 EXPORTS += [
     'nsdefs.h',
     'WindowHook.h',
     'WinUtils.h',
 ]
 
 EXPORTS.mozilla.widget += [
     'AudioSession.h',
+    'WinMessages.h',
 ]
 
 UNIFIED_SOURCES += [
     'AudioSession.cpp',
     'GfxInfo.cpp',
     'IEnumFE.cpp',
     'IMMHandler.cpp',
     'InkCollector.cpp',

--- a/widget/windows/nsWindowDefs.h
+++ b/widget/windows/nsWindowDefs.h
@@ -5,200 +5,44 @@
 
 #ifndef WindowDefs_h__
 #define WindowDefs_h__
 
 /*
  * nsWindowDefs - nsWindow related definitions, consts, and macros.
  */
 
+#include "mozilla/widget/WinMessages.h"
 #include "nsBaseWidget.h"
 #include "nsdefs.h"
 #include "resource.h"
 
 /**************************************************************
  *
  * SECTION: defines
  * 
  **************************************************************/
 
-// A magic APP message that can be sent to quit, sort of like a QUERYENDSESSION/ENDSESSION,
-// but without the query.
-#define MOZ_WM_APP_QUIT                   (WM_APP+0x0300)
-// Used as a "tracer" event to probe event loop latency.
-#define MOZ_WM_TRACE                      (WM_APP+0x0301)
-// Our internal message for WM_MOUSEWHEEL, WM_MOUSEHWHEEL, WM_VSCROLL and
-// WM_HSCROLL
-#define MOZ_WM_MOUSEVWHEEL                (WM_APP+0x0310)
-#define MOZ_WM_MOUSEHWHEEL                (WM_APP+0x0311)
-#define MOZ_WM_VSCROLL                    (WM_APP+0x0312)
-#define MOZ_WM_HSCROLL                    (WM_APP+0x0313)
-#define MOZ_WM_MOUSEWHEEL_FIRST           MOZ_WM_MOUSEVWHEEL
-#define MOZ_WM_MOUSEWHEEL_LAST            MOZ_WM_HSCROLL
-// If a popup window is being activated, we try to reactivate the previous
-// window with this message.
-#define MOZ_WM_REACTIVATE                 (WM_APP+0x0314)
-// If TSFTextStore needs to notify TSF/TIP of layout change later, this
-// message is posted.
-#define MOZ_WM_NOTIY_TSF_OF_LAYOUT_CHANGE (WM_APP+0x0315)
-// Internal message used in correcting backwards clock skew
-#define MOZ_WM_SKEWFIX                    (WM_APP+0x0316)
-// Internal message used for hiding the on-screen keyboard
-#define MOZ_WM_DISMISS_ONSCREEN_KEYBOARD  (WM_APP+0x0317)
-
-// Internal message for ensuring the file picker is visible on multi monitor
-// systems, and when the screen resolution changes.
-#define MOZ_WM_ENSUREVISIBLE              (WM_APP+0x374F)
-
-#ifndef SM_CXPADDEDBORDER
-#define SM_CXPADDEDBORDER                 92
-#endif
-
-// require WINVER >= 0x601
-#ifndef SM_MAXIMUMTOUCHES
-#define SM_MAXIMUMTOUCHES                 95
-#endif
-
-#ifndef WM_THEMECHANGED
-#define WM_THEMECHANGED                   0x031A
-#endif
-
-#ifndef WM_GETOBJECT
-#define WM_GETOBJECT                      0x03d
-#endif
-
-#ifndef PBT_APMRESUMEAUTOMATIC
-#define PBT_APMRESUMEAUTOMATIC            0x0012
-#endif
-
-#ifndef WM_MOUSEHWHEEL
-#define WM_MOUSEHWHEEL                    0x020E
-#endif
-
-#ifndef MOUSEEVENTF_HWHEEL
-#define MOUSEEVENTF_HWHEEL                0x01000
-#endif
-
-#ifndef WM_MOUSELEAVE
-#define WM_MOUSELEAVE                     0x02A3
-#endif
-
-#ifndef SPI_GETWHEELSCROLLCHARS
-#define SPI_GETWHEELSCROLLCHARS           0x006C
-#endif
-
-#ifndef SPI_SETWHEELSCROLLCHARS
-#define SPI_SETWHEELSCROLLCHARS           0x006D
-#endif
-
-#ifndef MAPVK_VSC_TO_VK
-#define MAPVK_VK_TO_VSC                   0
-#define MAPVK_VSC_TO_VK                   1
-#define MAPVK_VK_TO_CHAR                  2
-#define MAPVK_VSC_TO_VK_EX                3
-#define MAPVK_VK_TO_VSC_EX                4
-#endif
-
-#ifndef WM_DWMCOMPOSITIONCHANGED
-#define WM_DWMCOMPOSITIONCHANGED          0x031E
-#endif
-#ifndef WM_DWMNCRENDERINGCHANGED
-#define WM_DWMNCRENDERINGCHANGED          0x031F
-#endif
-#ifndef WM_DWMCOLORIZATIONCOLORCHANGED
-#define WM_DWMCOLORIZATIONCOLORCHANGED    0x0320
-#endif
-#ifndef WM_DWMWINDOWMAXIMIZEDCHANGE
-#define WM_DWMWINDOWMAXIMIZEDCHANGE       0x0321
-#endif
-
 // ConstrainPosition window positioning slop value
 #define kWindowPositionSlop               20
 
 // Origin of the system context menu when displayed in full screen mode
 #define MOZ_SYSCONTEXT_X_POS              20
 #define MOZ_SYSCONTEXT_Y_POS              20
 
-// Drop shadow window style
-#define CS_XP_DROPSHADOW                  0x00020000
-
 // Don't put more than this many rects in the dirty region, just fluff
 // out to the bounding-box if there are more
 #define MAX_RECTS_IN_REGION               100
 
-// App Command messages for IntelliMouse and Natural Keyboard Pro
-// These messages are not included in Visual C++ 6.0, but are in 7.0+
-#ifndef WM_APPCOMMAND
-#define WM_APPCOMMAND                     0x0319
-#endif
-
-#define FAPPCOMMAND_MASK                  0xF000
-
-#ifndef WM_GETTITLEBARINFOEX
-#define WM_GETTITLEBARINFOEX              0x033F
-#endif
-
-#ifndef CCHILDREN_TITLEBAR
-#define CCHILDREN_TITLEBAR                5
-#endif
-
-#ifndef APPCOMMAND_BROWSER_BACKWARD
-  #define APPCOMMAND_BROWSER_BACKWARD       1
-  #define APPCOMMAND_BROWSER_FORWARD        2
-  #define APPCOMMAND_BROWSER_REFRESH        3
-  #define APPCOMMAND_BROWSER_STOP           4
-  #define APPCOMMAND_BROWSER_SEARCH         5
-  #define APPCOMMAND_BROWSER_FAVORITES      6
-  #define APPCOMMAND_BROWSER_HOME           7
-
-  #define APPCOMMAND_MEDIA_NEXTTRACK        11
-  #define APPCOMMAND_MEDIA_PREVIOUSTRACK    12
-  #define APPCOMMAND_MEDIA_STOP             13
-  #define APPCOMMAND_MEDIA_PLAY_PAUSE       14
-
-  /* 
-   * Additional commands currently not in use.
-   *
-   *#define APPCOMMAND_VOLUME_MUTE            8
-   *#define APPCOMMAND_VOLUME_DOWN            9
-   *#define APPCOMMAND_VOLUME_UP              10
-   *#define APPCOMMAND_LAUNCH_MAIL            15
-   *#define APPCOMMAND_LAUNCH_MEDIA_SELECT    16
-   *#define APPCOMMAND_LAUNCH_APP1            17
-   *#define APPCOMMAND_LAUNCH_APP2            18
-   *#define APPCOMMAND_BASS_DOWN              19
-   *#define APPCOMMAND_BASS_BOOST             20
-   *#define APPCOMMAND_BASS_UP                21
-   *#define APPCOMMAND_TREBLE_DOWN            22
-   *#define APPCOMMAND_TREBLE_UP              23
-   *#define FAPPCOMMAND_MOUSE                 0x8000
-   *#define FAPPCOMMAND_KEY                   0
-   *#define FAPPCOMMAND_OEM                   0x1000
-   */
-
-  #define GET_APPCOMMAND_LPARAM(lParam)     ((short)(HIWORD(lParam) & ~FAPPCOMMAND_MASK))
-
-  /*
-   *#define GET_DEVICE_LPARAM(lParam)         ((WORD)(HIWORD(lParam) & FAPPCOMMAND_MASK))
-   *#define GET_MOUSEORKEY_LPARAM             GET_DEVICE_LPARAM
-   *#define GET_FLAGS_LPARAM(lParam)          (LOWORD(lParam))
-   *#define GET_KEYSTATE_LPARAM(lParam)       GET_FLAGS_LPARAM(lParam)
-   */
-#endif // #ifndef APPCOMMAND_BROWSER_BACKWARD
-
 //Tablet PC Mouse Input Source
 #define TABLET_INK_SIGNATURE 0xFFFFFF00
 #define TABLET_INK_CHECK     0xFF515700
 #define TABLET_INK_TOUCH     0x00000080
 #define MOUSE_INPUT_SOURCE() WinUtils::GetMouseInputSource()
 
-// Messages for fullscreen transition window
-#define WM_FULLSCREEN_TRANSITION_BEFORE     (WM_USER + 0)
-#define WM_FULLSCREEN_TRANSITION_AFTER      (WM_USER + 1)
-
 /**************************************************************
  *
  * SECTION: enums
  * 
  **************************************************************/
 
 // nsWindow::sCanQuit
 typedef enum