--- a/dom/plugins/base/PluginPRLibrary.cpp
+++ b/dom/plugins/base/PluginPRLibrary.cpp
@@ -274,16 +274,18 @@ PluginPRLibrary::GetImageContainer(NPP i
 nsresult
 PluginPRLibrary::IsRemoteDrawingCoreAnimation(NPP instance, bool *aDrawing)
 {
   nsNPAPIPluginInstance* inst = (nsNPAPIPluginInstance*)instance->ndata;
   NS_ENSURE_TRUE(inst, NS_ERROR_NULL_POINTER);
   *aDrawing = false; 
   return NS_OK;
 }
+#endif
+#if defined(XP_MACOSX) || defined(XP_WIN)
 nsresult
 PluginPRLibrary::ContentsScaleFactorChanged(NPP instance, double aContentsScaleFactor)
 {
   nsNPAPIPluginInstance* inst = (nsNPAPIPluginInstance*)instance->ndata;
   NS_ENSURE_TRUE(inst, NS_ERROR_NULL_POINTER);
   return NS_OK;
 }
 #endif

--- a/dom/plugins/base/PluginPRLibrary.h
+++ b/dom/plugins/base/PluginPRLibrary.h
@@ -109,16 +109,18 @@ public:
     virtual nsresult NPP_GetSitesWithData(nsCOMPtr<nsIGetSitesWithDataCallback> callback) override;
 
     virtual nsresult AsyncSetWindow(NPP aInstance, NPWindow* aWindow) override;
     virtual nsresult GetImageContainer(NPP aInstance, mozilla::layers::ImageContainer** aContainer) override;
     virtual nsresult GetImageSize(NPP aInstance, nsIntSize* aSize) override;
     virtual bool IsOOP() override { return false; }
 #if defined(XP_MACOSX)
     virtual nsresult IsRemoteDrawingCoreAnimation(NPP aInstance, bool* aDrawing) override;
+#endif
+#if defined(XP_MACOSX) || defined(XP_WIN)
     virtual nsresult ContentsScaleFactorChanged(NPP aInstance, double aContentsScaleFactor) override;
 #endif
     virtual nsresult SetBackgroundUnknown(NPP instance) override;
     virtual nsresult BeginUpdateBackground(NPP instance, const nsIntRect&,
                                            DrawTarget** aDrawTarget) override;
     virtual nsresult EndUpdateBackground(NPP instance,
                                          const nsIntRect&) override;
     virtual void DidComposite(NPP aInstance) override { }

--- a/dom/plugins/base/npapi.h
+++ b/dom/plugins/base/npapi.h
@@ -411,18 +411,20 @@ typedef enum {
 
   NPNVsupportsAdvancedKeyHandling = 21,
 
   NPNVdocumentOrigin = 22,
 
   NPNVCSSZoomFactor = 23,
 
   NPNVpluginDrawingModel = 1000 /* Get the current drawing model (NPDrawingModel) */
+#if defined(XP_MACOSX) || defined(XP_WIN)
+  , NPNVcontentsScaleFactor = 1001
+#endif
 #if defined(XP_MACOSX)
-  , NPNVcontentsScaleFactor = 1001
 #ifndef NP_NO_QUICKDRAW
   , NPNVsupportsQuickDrawBool = 2000
 #endif
   , NPNVsupportsCoreGraphicsBool = 2001
   , NPNVsupportsOpenGLBool = 2002
   , NPNVsupportsCoreAnimationBool = 2003
   , NPNVsupportsInvalidatingCoreAnimationBool = 2004
 #endif

--- a/dom/plugins/base/nsNPAPIPlugin.cpp
+++ b/dom/plugins/base/nsNPAPIPlugin.cpp
@@ -2008,17 +2008,19 @@ NPError
 
     return NPERR_NO_ERROR;
   }
 
   case NPNVsupportsUpdatedCocoaTextInputBool: {
     *(NPBool*)result = true;
     return NPERR_NO_ERROR;
   }
-
+#endif
+
+#if defined(XP_MACOSX) || defined(XP_WIN)
   case NPNVcontentsScaleFactor: {
     nsNPAPIPluginInstance *inst =
       (nsNPAPIPluginInstance *) (npp ? npp->ndata : nullptr);
     double scaleFactor = inst ? inst->GetContentsScaleFactor() : 1.0;
     *(double*)result = scaleFactor;
     return NPERR_NO_ERROR;
   }
 #endif

--- a/dom/plugins/base/nsNPAPIPluginInstance.cpp
+++ b/dom/plugins/base/nsNPAPIPluginInstance.cpp
@@ -1000,17 +1000,17 @@ nsresult nsNPAPIPluginInstance::IsRemote
 #else
   return NS_ERROR_FAILURE;
 #endif
 }
 
 nsresult
 nsNPAPIPluginInstance::ContentsScaleFactorChanged(double aContentsScaleFactor)
 {
-#ifdef XP_MACOSX
+#if defined(XP_MACOSX) || defined(XP_WIN)
   if (!mPlugin)
       return NS_ERROR_FAILURE;
 
   PluginLibrary* library = mPlugin->GetLibrary();
   if (!library)
       return NS_ERROR_FAILURE;
 
   // We only need to call this if the plugin is running OOP.

--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -1348,24 +1348,16 @@ bool nsPluginInstanceOwner::IsRemoteDraw
 
   bool coreAnimation;
   if (!NS_SUCCEEDED(mInstance->IsRemoteDrawingCoreAnimation(&coreAnimation)))
     return false;
 
   return coreAnimation;
 }
 
-nsresult nsPluginInstanceOwner::ContentsScaleFactorChanged(double aContentsScaleFactor)
-{
-  if (!mInstance) {
-    return NS_ERROR_NULL_POINTER;
-  }
-  return mInstance->ContentsScaleFactorChanged(aContentsScaleFactor);
-}
-
 NPEventModel nsPluginInstanceOwner::GetEventModel()
 {
   return mEventModel;
 }
 
 #define DEFAULT_REFRESH_RATE 20 // 50 FPS
 
 nsCOMPtr<nsITimer>               *nsPluginInstanceOwner::sCATimer = nullptr;
@@ -1446,16 +1438,26 @@ void nsPluginInstanceOwner::RemoveFromCA
 void nsPluginInstanceOwner::SetPluginPort()
 {
   void* pluginPort = GetPluginPort();
   if (!pluginPort || !mPluginWindow)
     return;
   mPluginWindow->window = pluginPort;
 }
 #endif
+#if defined(XP_MACOSX) || defined(XP_WIN)
+nsresult nsPluginInstanceOwner::ContentsScaleFactorChanged(double aContentsScaleFactor)
+{
+  if (!mInstance) {
+    return NS_ERROR_NULL_POINTER;
+  }
+  return mInstance->ContentsScaleFactorChanged(aContentsScaleFactor);
+}
+#endif
+
 
 // static
 uint32_t
 nsPluginInstanceOwner::GetEventloopNestingLevel()
 {
   nsCOMPtr<nsIAppShell> appShell = do_GetService(kAppShellCID);
   uint32_t currentLevel = 0;
   if (appShell) {
@@ -3618,17 +3620,17 @@ nsPluginInstanceOwner::UpdateWindowVisib
   mPluginWindowVisible = aVisible;
   UpdateWindowPositionAndClipRect(true);
 }
 #endif // XP_MACOSX
 
 void
 nsPluginInstanceOwner::ResolutionMayHaveChanged()
 {
-#ifdef XP_MACOSX
+#if defined(XP_MACOSX) || defined(XP_WIN)
   double scaleFactor = 1.0;
   GetContentsScaleFactor(&scaleFactor);
   if (scaleFactor != mLastScaleFactor) {
     ContentsScaleFactorChanged(scaleFactor);
     mLastScaleFactor = scaleFactor;
   }
 #endif
   float zoomFactor = 1.0;
@@ -3704,17 +3706,17 @@ nsPluginInstanceOwner::CallSetWindow()
 NS_IMETHODIMP
 nsPluginInstanceOwner::GetContentsScaleFactor(double *result)
 {
   NS_ENSURE_ARG_POINTER(result);
   double scaleFactor = 1.0;
   // On Mac, device pixels need to be translated to (and from) "display pixels"
   // for plugins. On other platforms, plugin coordinates are always in device
   // pixels.
-#if defined(XP_MACOSX)
+#if defined(XP_MACOSX) || defined(XP_WIN)
   nsCOMPtr<nsIContent> content = do_QueryReferent(mContent);
   nsIPresShell* presShell = nsContentUtils::FindPresShellForDocument(content->OwnerDoc());
   if (presShell) {
     scaleFactor = double(nsPresContext::AppUnitsPerCSSPixel())/
       presShell->GetPresContext()->DeviceContext()->AppUnitsPerDevPixelAtUnitFullZoom();
   }
 #endif
   *result = scaleFactor;

--- a/dom/plugins/base/nsPluginInstanceOwner.h
+++ b/dom/plugins/base/nsPluginInstanceOwner.h
@@ -136,33 +136,37 @@ public:
   enum { ePluginPaintEnable, ePluginPaintDisable };
 
   void WindowFocusMayHaveChanged();
 
   bool WindowIsActive();
   void SendWindowFocusChanged(bool aIsActive);
   NPDrawingModel GetDrawingModel();
   bool IsRemoteDrawingCoreAnimation();
-  nsresult ContentsScaleFactorChanged(double aContentsScaleFactor);
+
   NPEventModel GetEventModel();
   static void CARefresh(nsITimer *aTimer, void *aClosure);
   void AddToCARefreshTimer();
   void RemoveFromCARefreshTimer();
   // This calls into the plugin (NPP_SetWindow) and can run script.
   void FixUpPluginWindow(int32_t inPaintState);
   void HidePluginWindow();
   // Set plugin port info in the plugin (in the 'window' member of the
   // NPWindow structure passed to the plugin by SetWindow()).
   void SetPluginPort();
 #else // XP_MACOSX
   void UpdateWindowPositionAndClipRect(bool aSetWindow);
   void UpdateWindowVisibility(bool aVisible);
 #endif // XP_MACOSX
 
   void ResolutionMayHaveChanged();
+#if defined(XP_MACOSX) || defined(XP_WIN)
+  nsresult ContentsScaleFactorChanged(double aContentsScaleFactor);
+#endif
+
   void UpdateDocumentActiveState(bool aIsActive);
 
   void SetFrame(nsPluginFrame *aFrame);
   nsPluginFrame* GetFrame();
 
   uint32_t GetLastEventloopNestingLevel() const {
     return mLastEventloopNestingLevel; 
   }
@@ -332,20 +336,20 @@ private:
   RefPtr<nsPluginHost>      mPluginHost;
   
 #ifdef XP_MACOSX
   static nsCOMPtr<nsITimer>                *sCATimer;
   static nsTArray<nsPluginInstanceOwner*>  *sCARefreshListeners;
   bool                                      mSentInitialTopLevelWindowEvent;
   bool                                      mLastWindowIsActive;
   bool                                      mLastContentFocused;
-  double                                    mLastScaleFactor;
   // True if, the next time the window is activated, we should blur ourselves.
   bool                                      mShouldBlurOnActivate;
 #endif
+  double                                    mLastScaleFactor;
   double                                    mLastCSSZoomFactor;
   // Initially, the event loop nesting level we were created on, it's updated
   // if we detect the appshell is on a lower level as long as we're not stopped.
   // We delay DoStopPlugin() until the appshell reaches this level or lower.
   uint32_t                    mLastEventloopNestingLevel;
   bool                        mContentFocused;
   bool                        mWidgetVisible;    // used on Mac to store our widget's visible state
 #ifdef MOZ_X11

--- a/dom/plugins/ipc/NPEventWindows.h
+++ b/dom/plugins/ipc/NPEventWindows.h
@@ -20,16 +20,17 @@ namespace plugins {
 // the stack so that we don't need to worry about managing the memory.
 struct NPRemoteEvent
 {
     NPEvent event;
     union {
         RECT rect;
         WINDOWPOS windowpos;
     } lParamData;
+    double contentsScaleFactor;
 };
 
 }
 
 }
 
 namespace IPC {
 

--- a/dom/plugins/ipc/PluginInstanceChild.cpp
+++ b/dom/plugins/ipc/PluginInstanceChild.cpp
@@ -135,17 +135,17 @@ PluginInstanceChild::PluginInstanceChild
                                          const uint16_t& aMode,
                                          const InfallibleTArray<nsCString>& aNames,
                                          const InfallibleTArray<nsCString>& aValues)
     : mPluginIface(aPluginIface)
     , mMimeType(aMimeType)
     , mMode(aMode)
     , mNames(aNames)
     , mValues(aValues)
-#if defined(XP_DARWIN)
+#if defined(XP_DARWIN) || defined (XP_WIN)
     , mContentsScaleFactor(1.0)
 #endif
     , mPostingKeyEvents(0)
     , mPostingKeyEventsOutdated(0)
     , mDrawingModel(kDefaultDrawingModel)
     , mCurrentDirectSurface(nullptr)
     , mAsyncInvalidateMutex("PluginInstanceChild::mAsyncInvalidateMutex")
     , mAsyncInvalidateTask(0)
@@ -528,22 +528,24 @@ PluginInstanceChild::NPN_GetValue(NPNVar
     }
 
 #ifndef NP_NO_QUICKDRAW
     case NPNVsupportsQuickDrawBool: {
         *((NPBool*)aValue) = false;
         return NPERR_NO_ERROR;
     }
 #endif /* NP_NO_QUICKDRAW */
-
+#endif /* XP_MACOSX */
+
+#if defined(XP_MACOSX) || defined(XP_WIN)
     case NPNVcontentsScaleFactor: {
         *static_cast<double*>(aValue) = mContentsScaleFactor;
         return NPERR_NO_ERROR;
     }
-#endif /* XP_MACOSX */
+#endif /* defined(XP_MACOSX) || defined(XP_WIN) */
 
     case NPNVCSSZoomFactor: {
         *static_cast<double*>(aValue) = mCSSZoomFactor;
         return NPERR_NO_ERROR;
     }
 #ifdef DEBUG
     case NPNVjavascriptEnabledBool:
     case NPNVasdEnabledBool:
@@ -865,33 +867,36 @@ PluginInstanceChild::AnswerNPP_HandleEve
     if (GraphicsExpose == event.event.type)
         PLUGIN_LOG_DEBUG(("  received drawable 0x%lx\n",
                           event.event.xgraphicsexpose.drawable));
 #endif
 
 #ifdef XP_MACOSX
     // Mac OS X does not define an NPEvent structure. It defines more specific types.
     NPCocoaEvent evcopy = event.event;
-    // event.contentsScaleFactor <= 0 is a signal we shouldn't use it,
-    // for example when AnswerNPP_HandleEvent() is called from elsewhere
-    // in the child process (not via rpc code from the parent process).
-    if (event.contentsScaleFactor > 0) {
-      mContentsScaleFactor = event.contentsScaleFactor;
-    }
 
     // Make sure we reset mCurrentEvent in case of an exception
     AutoRestore<const NPCocoaEvent*> savePreviousEvent(mCurrentEvent);
 
     // Track the current event for NPN_PopUpContextMenu.
     mCurrentEvent = &event.event;
 #else
     // Make a copy since we may modify values.
     NPEvent evcopy = event.event;
 #endif
 
+#if defined(XP_MACOSX) || defined(XP_WIN)
+    // event.contentsScaleFactor <= 0 is a signal we shouldn't use it,
+    // for example when AnswerNPP_HandleEvent() is called from elsewhere
+    // in the child process (not via rpc code from the parent process).
+    if (event.contentsScaleFactor > 0) {
+      mContentsScaleFactor = event.contentsScaleFactor;
+    }
+#endif
+
 #ifdef OS_WIN
     // FIXME/bug 567645: temporarily drop the "dummy event" on the floor
     if (WM_NULL == evcopy.event)
         return true;
 
     *handled = WinlessHandleEvent(evcopy);
     return true;
 #endif
@@ -1127,27 +1132,29 @@ PluginInstanceChild::RecvWindowPosChange
     NS_RUNTIMEABORT("WindowPosChanged is a windows-only message");
     return false;
 #endif
 }
 
 bool
 PluginInstanceChild::RecvContentsScaleFactorChanged(const double& aContentsScaleFactor)
 {
-#ifdef XP_MACOSX
+#if defined(XP_MACOSX) || defined(XP_WIN)
     mContentsScaleFactor = aContentsScaleFactor;
+#if defined(XP_MACOSX)
     if (mShContext) {
         // Release the shared context so that it is reallocated
         // with the new size. 
         ::CGContextRelease(mShContext);
         mShContext = nullptr;
     }
+#endif
     return true;
 #else
-    NS_RUNTIMEABORT("ContentsScaleFactorChanged is an OSX-only message");
+    NS_RUNTIMEABORT("ContentsScaleFactorChanged is an Windows or OSX only message");
     return false;
 #endif
 }
 
 #if defined(MOZ_X11) && defined(XP_UNIX) && !defined(XP_MACOSX)
 // Create a new window from NPWindow
 bool PluginInstanceChild::CreateWindow(const NPRemoteWindow& aWindow)
 { 
@@ -1332,16 +1339,17 @@ PluginInstanceChild::AnswerNPP_SetWindow
           SizePluginWindow(aWindow.width, aWindow.height);
 
           mWindow.window = (void*)mPluginWindowHWND;
           mWindow.x = aWindow.x;
           mWindow.y = aWindow.y;
           mWindow.width = aWindow.width;
           mWindow.height = aWindow.height;
           mWindow.type = aWindow.type;
+          mContentsScaleFactor = aWindow.contentsScaleFactor;
 
           if (mPluginIface->setwindow) {
               SetProp(mPluginWindowHWND, kPluginIgnoreSubclassProperty, (HANDLE)1);
               (void) mPluginIface->setwindow(&mData, &mWindow);
               WNDPROC wndProc = reinterpret_cast<WNDPROC>(
                   GetWindowLongPtr(mPluginWindowHWND, GWLP_WNDPROC));
               if (wndProc != PluginWindowProc) {
                   mPluginWndProc = reinterpret_cast<WNDPROC>(
@@ -3323,17 +3331,17 @@ PluginInstanceChild::DoAsyncSetWindow(co
         mAccumulatedInvalidRect = nsIntRect(0, 0, aWindow.width, aWindow.height);
 
     mWindow.x = aWindow.x;
     mWindow.y = aWindow.y;
     mWindow.width = aWindow.width;
     mWindow.height = aWindow.height;
     mWindow.clipRect = aWindow.clipRect;
     mWindow.type = aWindow.type;
-#ifdef XP_MACOSX
+#if defined(XP_MACOSX) || defined(XP_WIN)
     mContentsScaleFactor = aWindow.contentsScaleFactor;
 #endif
 
     if (GetQuirks() & QUIRK_SILVERLIGHT_DEFAULT_TRANSPARENT)
         mIsTransparent = true;
 
     mLayersRendering = true;
     mSurfaceType = aSurfaceType;

--- a/dom/plugins/ipc/PluginInstanceChild.h
+++ b/dom/plugins/ipc/PluginInstanceChild.h
@@ -405,17 +405,17 @@ private:
 #endif // #if defined(OS_WIN)
     const NPPluginFuncs* mPluginIface;
     nsCString                   mMimeType;
     uint16_t                    mMode;
     InfallibleTArray<nsCString> mNames;
     InfallibleTArray<nsCString> mValues;
     NPP_t mData;
     NPWindow mWindow;
-#if defined(XP_DARWIN)
+#if defined(XP_DARWIN) || defined(XP_WIN)
     double mContentsScaleFactor;
 #endif
     double mCSSZoomFactor;
     uint32_t mPostingKeyEvents;
     uint32_t mPostingKeyEventsOutdated;
     int16_t               mDrawingModel;
 
     NPAsyncSurface* mCurrentDirectSurface;

--- a/dom/plugins/ipc/PluginInstanceParent.cpp
+++ b/dom/plugins/ipc/PluginInstanceParent.cpp
@@ -987,17 +987,17 @@ PluginInstanceParent::AsyncSetWindow(NPW
     mWindowType = aWindow->type;
     window.window = reinterpret_cast<uint64_t>(aWindow->window);
     window.x = aWindow->x;
     window.y = aWindow->y;
     window.width = aWindow->width;
     window.height = aWindow->height;
     window.clipRect = aWindow->clipRect;
     window.type = aWindow->type;
-#ifdef XP_MACOSX
+#if defined(XP_MACOSX) || defined(XP_WIN)
     double scaleFactor = 1.0;
     mNPNIface->getvalue(mNPP, NPNVcontentsScaleFactor, &scaleFactor);
     window.contentsScaleFactor = scaleFactor;
 #endif
 
 #if defined(OS_WIN)
     MaybeCreateChildPopupSurrogate();
 #endif
@@ -1101,17 +1101,18 @@ PluginInstanceParent::DidComposite()
 #ifdef XP_MACOSX
 nsresult
 PluginInstanceParent::IsRemoteDrawingCoreAnimation(bool *aDrawing)
 {
     *aDrawing = (NPDrawingModelCoreAnimation == (NPDrawingModel)mDrawingModel ||
                  NPDrawingModelInvalidatingCoreAnimation == (NPDrawingModel)mDrawingModel);
     return NS_OK;
 }
-
+#endif
+#if defined(XP_MACOSX) || defined(XP_WIN)
 nsresult
 PluginInstanceParent::ContentsScaleFactorChanged(double aContentsScaleFactor)
 {
     bool rv = SendContentsScaleFactorChanged(aContentsScaleFactor);
     return rv ? NS_OK : NS_ERROR_FAILURE;
 }
 #endif // #ifdef XP_MACOSX
 
@@ -1360,22 +1361,23 @@ PluginInstanceParent::NPP_SetWindow(cons
     window.x = aWindow->x;
     window.y = aWindow->y;
     window.width = aWindow->width;
     window.height = aWindow->height;
     window.clipRect = aWindow->clipRect; // MacOS specific
     window.type = aWindow->type;
 #endif
 
-#if defined(XP_MACOSX)
+#if defined(XP_MACOSX) || defined(XP_WIN)
     double floatScaleFactor = 1.0;
     mNPNIface->getvalue(mNPP, NPNVcontentsScaleFactor, &floatScaleFactor);
     int scaleFactor = ceil(floatScaleFactor);
     window.contentsScaleFactor = floatScaleFactor;
-
+#endif
+#if defined(XP_MACOSX)
     if (mShWidth != window.width * scaleFactor || mShHeight != window.height * scaleFactor) {
         if (mDrawingModel == NPDrawingModelCoreAnimation ||
             mDrawingModel == NPDrawingModelInvalidatingCoreAnimation) {
             mIOSurface = MacIOSurface::CreateIOSurface(window.width, window.height,
                                                        floatScaleFactor);
         } else if (uint32_t(mShWidth * mShHeight) !=
                    window.width * scaleFactor * window.height * scaleFactor) {
             if (mShWidth != 0 && mShHeight != 0) {
@@ -1560,17 +1562,17 @@ PluginInstanceParent::NPP_HandleEvent(vo
 
 #if defined(XP_MACOSX)
     NPCocoaEvent* npevent = reinterpret_cast<NPCocoaEvent*>(event);
 #else
     NPEvent* npevent = reinterpret_cast<NPEvent*>(event);
 #endif
     NPRemoteEvent npremoteevent;
     npremoteevent.event = *npevent;
-#if defined(XP_MACOSX)
+#if defined(XP_MACOSX) || defined(XP_WIN)
     double scaleFactor = 1.0;
     mNPNIface->getvalue(mNPP, NPNVcontentsScaleFactor, &scaleFactor);
     npremoteevent.contentsScaleFactor = scaleFactor;
 #endif
     int16_t handled = 0;
 
 #if defined(OS_WIN)
     if (mWindowType == NPWindowTypeDrawable) {

--- a/dom/plugins/ipc/PluginInstanceParent.h
+++ b/dom/plugins/ipc/PluginInstanceParent.h
@@ -319,16 +319,18 @@ public:
     virtual bool
     AnswerPluginFocusChange(const bool& gotFocus) override;
 
     nsresult AsyncSetWindow(NPWindow* window);
     nsresult GetImageContainer(mozilla::layers::ImageContainer** aContainer);
     nsresult GetImageSize(nsIntSize* aSize);
 #ifdef XP_MACOSX
     nsresult IsRemoteDrawingCoreAnimation(bool *aDrawing);
+#endif
+#if defined(XP_MACOSX) || defined(XP_WIN)
     nsresult ContentsScaleFactorChanged(double aContentsScaleFactor);
 #endif
     nsresult SetBackgroundUnknown();
     nsresult BeginUpdateBackground(const nsIntRect& aRect,
                                    DrawTarget** aDrawTarget);
     nsresult EndUpdateBackground(const nsIntRect& aRect);
 #if defined(XP_WIN)
     nsresult SetScrollCaptureId(uint64_t aScrollCaptureId);

--- a/dom/plugins/ipc/PluginLibrary.h
+++ b/dom/plugins/ipc/PluginLibrary.h
@@ -80,16 +80,18 @@ public:
 
   virtual nsresult AsyncSetWindow(NPP instance, NPWindow* window) = 0;
   virtual nsresult GetImageContainer(NPP instance, mozilla::layers::ImageContainer** aContainer) = 0;
   virtual nsresult GetImageSize(NPP instance, nsIntSize* aSize) = 0;
   virtual void DidComposite(NPP instance) = 0;
   virtual bool IsOOP() = 0;
 #if defined(XP_MACOSX)
   virtual nsresult IsRemoteDrawingCoreAnimation(NPP instance, bool *aDrawing) = 0;
+#endif
+#if defined(XP_MACOSX) || defined(XP_WIN)
   virtual nsresult ContentsScaleFactorChanged(NPP instance, double aContentsScaleFactor) = 0;
 #endif
 #if defined(XP_WIN)
     virtual nsresult GetScrollCaptureContainer(NPP aInstance, mozilla::layers::ImageContainer** aContainer) = 0;
 #endif
   virtual nsresult HandledWindowedPluginKeyEvent(
                      NPP aInstance,
                      const mozilla::NativeEventData& aNativeKeyData,

--- a/dom/plugins/ipc/PluginMessageUtils.h
+++ b/dom/plugins/ipc/PluginMessageUtils.h
@@ -88,17 +88,17 @@ struct NPRemoteWindow
   uint32_t width;
   uint32_t height;
   NPRect clipRect;
   NPWindowType type;
 #if defined(MOZ_X11) && defined(XP_UNIX) && !defined(XP_MACOSX)
   VisualID visualID;
   Colormap colormap;
 #endif /* XP_UNIX */
-#if defined(XP_MACOSX)
+#if defined(XP_MACOSX) || defined(XP_WIN)
   double contentsScaleFactor;
 #endif
 };
 
 #ifdef XP_WIN
 typedef HWND NativeWindowHandle;
 #elif defined(MOZ_X11)
 typedef XID NativeWindowHandle;
@@ -341,17 +341,17 @@ struct ParamTraits<mozilla::plugins::NPR
     WriteParam(aMsg, aParam.width);
     WriteParam(aMsg, aParam.height);
     WriteParam(aMsg, aParam.clipRect);
     WriteParam(aMsg, aParam.type);
 #if defined(MOZ_X11) && defined(XP_UNIX) && !defined(XP_MACOSX)
     aMsg->WriteULong(aParam.visualID);
     aMsg->WriteULong(aParam.colormap);
 #endif
-#if defined(XP_MACOSX)
+#if defined(XP_MACOSX) || defined(XP_WIN)
     aMsg->WriteDouble(aParam.contentsScaleFactor);
 #endif
   }
 
   static bool Read(const Message* aMsg, PickleIterator* aIter, paramType* aResult)
   {
     uint64_t window;
     int32_t x, y;
@@ -370,34 +370,34 @@ struct ParamTraits<mozilla::plugins::NPR
 #if defined(MOZ_X11) && defined(XP_UNIX) && !defined(XP_MACOSX)
     unsigned long visualID;
     unsigned long colormap;
     if (!(aMsg->ReadULong(aIter, &visualID) &&
           aMsg->ReadULong(aIter, &colormap)))
       return false;
 #endif
 
-#if defined(XP_MACOSX)
+#if defined(XP_MACOSX) || defined(XP_WIN)
     double contentsScaleFactor;
     if (!aMsg->ReadDouble(aIter, &contentsScaleFactor))
       return false;
 #endif
 
     aResult->window = window;
     aResult->x = x;
     aResult->y = y;
     aResult->width = width;
     aResult->height = height;
     aResult->clipRect = clipRect;
     aResult->type = type;
 #if defined(MOZ_X11) && defined(XP_UNIX) && !defined(XP_MACOSX)
     aResult->visualID = visualID;
     aResult->colormap = colormap;
 #endif
-#if defined(XP_MACOSX)
+#if defined(XP_MACOSX) || defined(XP_WIN)
     aResult->contentsScaleFactor = contentsScaleFactor;
 #endif
     return true;
   }
 
   static void Log(const paramType& aParam, std::wstring* aLog)
   {
     aLog->append(StringPrintf(L"[%u, %d, %d, %u, %u, %d",

--- a/dom/plugins/ipc/PluginModuleParent.cpp
+++ b/dom/plugins/ipc/PluginModuleParent.cpp
@@ -2850,17 +2850,18 @@ nsresult
 PluginModuleParent::IsRemoteDrawingCoreAnimation(NPP instance, bool *aDrawing)
 {
     PluginInstanceParent* i = PluginInstanceParent::Cast(instance);
     if (!i)
         return NS_ERROR_FAILURE;
 
     return i->IsRemoteDrawingCoreAnimation(aDrawing);
 }
-
+#endif
+#if defined(XP_MACOSX) || defined(XP_WIN)
 nsresult
 PluginModuleParent::ContentsScaleFactorChanged(NPP instance, double aContentsScaleFactor)
 {
     PluginInstanceParent* i = PluginInstanceParent::Cast(instance);
     if (!i)
         return NS_ERROR_FAILURE;
 
     return i->ContentsScaleFactorChanged(aContentsScaleFactor);

--- a/dom/plugins/ipc/PluginModuleParent.h
+++ b/dom/plugins/ipc/PluginModuleParent.h
@@ -300,16 +300,18 @@ private:
     nsCString mPluginFilename;
     int mQuirks;
     void InitQuirksModes(const nsCString& aMimeType);
 
 public:
 
 #if defined(XP_MACOSX)
     virtual nsresult IsRemoteDrawingCoreAnimation(NPP instance, bool *aDrawing) override;
+#endif
+#if defined(XP_MACOSX) || defined(XP_WIN)
     virtual nsresult ContentsScaleFactorChanged(NPP instance, double aContentsScaleFactor) override;
 #endif
 
     void InitAsyncSurrogates();
 
     layers::TextureClientRecycleAllocator* EnsureTextureAllocator();
 
 protected:

--- a/layout/generic/nsPluginFrame.cpp
+++ b/layout/generic/nsPluginFrame.cpp
@@ -565,25 +565,33 @@ nsPluginFrame::FixupWindow(const nsSize&
 
   NS_ENSURE_TRUE_VOID(window);
 
   bool windowless = (window->type == NPWindowTypeDrawable);
 
   nsIntPoint origin = GetWindowOriginInPixels(windowless);
 
   // window must be in "display pixels"
+#if defined(XP_MACOSX)
+  // window must be in "display pixels"
   double scaleFactor = 1.0;
   if (NS_FAILED(mInstanceOwner->GetContentsScaleFactor(&scaleFactor))) {
     scaleFactor = 1.0;
   }
   int intScaleFactor = ceil(scaleFactor);
   window->x = origin.x / intScaleFactor;
   window->y = origin.y / intScaleFactor;
   window->width = presContext->AppUnitsToDevPixels(aSize.width) / intScaleFactor;
   window->height = presContext->AppUnitsToDevPixels(aSize.height) / intScaleFactor;
+#else
+  window->x = origin.x;
+  window->y = origin.y;
+  window->width = presContext->AppUnitsToDevPixels(aSize.width);
+  window->height = presContext->AppUnitsToDevPixels(aSize.height);
+#endif
 
 #ifndef XP_MACOSX
   mInstanceOwner->UpdateWindowPositionAndClipRect(false);
 #endif
 
   NotifyPluginReflowObservers();
 }
 
@@ -634,27 +642,34 @@ nsPluginFrame::CallSetWindow(bool aCheck
   nsIntRect intBounds = bounds.ToNearestPixels(appUnitsPerDevPixel);
 
   // In e10s, this returns the offset to the top level window, in non-e10s
   // it return 0,0.
   LayoutDeviceIntPoint intOffset = GetRemoteTabChromeOffset();
   intBounds.x += intOffset.x;
   intBounds.y += intOffset.y;
 
+#if defined(XP_MACOSX)
   // window must be in "display pixels"
   double scaleFactor = 1.0;
   if (NS_FAILED(instanceOwnerRef->GetContentsScaleFactor(&scaleFactor))) {
     scaleFactor = 1.0;
   }
+
   size_t intScaleFactor = ceil(scaleFactor);
   window->x = intBounds.x / intScaleFactor;
   window->y = intBounds.y / intScaleFactor;
   window->width = intBounds.width / intScaleFactor;
   window->height = intBounds.height / intScaleFactor;
-
+#else
+  window->x = intBounds.x;
+  window->y = intBounds.y;
+  window->width = intBounds.width;
+  window->height = intBounds.height;
+#endif
   // BE CAREFUL: By the time we get here the PluginFrame is sometimes destroyed
   // and poisoned. If we reference local fields (implicit this deref),
   // we will crash.
   instanceOwnerRef->ResolutionMayHaveChanged();
 
   // This will call pi->SetWindow and take care of window subclassing
   // if needed, see bug 132759. Calling SetWindow can destroy this frame
   // so check for that before doing anything else with this frame's memory.
@@ -1437,22 +1452,29 @@ nsPluginFrame::BuildLayer(nsDisplayListB
   NPWindow* window = nullptr;
   mInstanceOwner->GetWindow(window);
   if (!window)
     return nullptr;
 
   if (window->width <= 0 || window->height <= 0)
     return nullptr;
 
+#if defined(XP_MACOSX)
   // window is in "display pixels", but size needs to be in device pixels
+  // window must be in "display pixels"
   double scaleFactor = 1.0;
   if (NS_FAILED(mInstanceOwner->GetContentsScaleFactor(&scaleFactor))) {
     scaleFactor = 1.0;
   }
-  int intScaleFactor = ceil(scaleFactor);
+
+  size_t intScaleFactor = ceil(scaleFactor);
+#else
+  size_t intScaleFactor = 1;
+#endif
+
   IntSize size(window->width * intScaleFactor, window->height * intScaleFactor);
 
   nsRect area = GetContentRectRelativeToSelf() + aItem->ToReferenceFrame();
   gfxRect r = nsLayoutUtils::RectToGfxRect(area, PresContext()->AppUnitsPerDevPixel());
   // to provide crisper and faster drawing.
   r.Round();
   RefPtr<Layer> layer =
     (aManager->GetLayerBuilder()->GetLeafLayerFor(aBuilder, aItem));