--- a/dom/plugins/PPluginInstance.ipdl
+++ b/dom/plugins/PPluginInstance.ipdl
@@ -164,22 +164,24 @@ parent:
    */
   rpc PStreamNotify(nsCString url, nsCString target, bool post,
                     nsCString buffer, bool file)
     returns (NPError result);
 
   async NPN_InvalidateRect(NPRect rect);
 
   // Give |newSurface|, containing this instance's updated pixels, to
-  // the browser for compositing.  Get back |prevSurface|, containing
-  // old pixels, to be recycled
+  // the browser for compositing.  When this method returns, any surface 
+  // previously passed to Show may be destroyed.
+  //
   // @param rect - actually updated rectangle, comparing to prevSurface content
   //               could be used for partial render of layer to topLevel context
   // @param newSurface - remotable surface
-  // @param prevSurface - return surface for recycling
+  // @param prevSurface - if the previous surface was shared-memory, returns
+  //                      the shmem for reuse
   sync Show(NPRect updatedRect, SurfaceDescriptor newSurface)
     returns (SurfaceDescriptor prevSurface);
 
   rpc NPN_PushPopupsEnabledState(bool aState);
 
   rpc NPN_PopPopupsEnabledState();
 
   rpc NPN_GetValueForURL(NPNURLVariable variable, nsCString url)

--- a/dom/plugins/PluginInstanceChild.cpp
+++ b/dom/plugins/PluginInstanceChild.cpp
@@ -2478,34 +2478,37 @@ PluginInstanceChild::ShowPluginFrame()
     if (mDoAlphaExtraction) {
         PaintRectWithAlphaExtraction(rect, mCurrentSurface);
     } else {
         PaintRectToSurface(rect, mCurrentSurface, gfxRGBA(0.0, 0.0, 0.0, 0.0));
     }
 
     NPRect r = { rect.y, rect.x, rect.YMost(), rect.XMost() };
     SurfaceDescriptor currSurf;
-    SurfaceDescriptor outSurf = null_t();
 #ifdef MOZ_X11
     if (mCurrentSurface->GetType() == gfxASurface::SurfaceTypeXlib) {
         gfxXlibSurface *xsurf = static_cast<gfxXlibSurface*>(mCurrentSurface.get());
         currSurf = SurfaceDescriptorX11(xsurf->XDrawable(), xsurf->XRenderFormat()->id,
                                         mCurrentSurface->GetSize());
         // Need to sync all pending x-paint requests
         // before giving drawable to another process
         XSync(mWsInfo.display, False);
     } else
 #endif
     if (gfxSharedImageSurface::IsSharedImage(mCurrentSurface)) {
         currSurf = static_cast<gfxSharedImageSurface*>(mCurrentSurface.get())->GetShmem();
     } else {
         NS_RUNTIMEABORT("Surface type is not remotable");
         return false;
     }
-    if (!SendShow(r, currSurf, &outSurf)) {
+
+    // Unused, except to possibly return a shmem to us
+    SurfaceDescriptor returnSurf;
+
+    if (!SendShow(r, currSurf, &returnSurf)) {
         return false;
     }
 
     nsRefPtr<gfxASurface> tmp = mCurrentSurface;
     mCurrentSurface = mBackSurface;
     mBackSurface = tmp;
     // Outdated back surface... not usable anymore due to changed plugin size.
     // Dropping obsolete surface

--- a/dom/plugins/PluginInstanceParent.cpp
+++ b/dom/plugins/PluginInstanceParent.cpp
@@ -493,41 +493,24 @@ PluginInstanceParent::RecvShow(const NPR
             XRenderFindFormat(DefaultXDisplay(), PictFormatID, &pf, 0);
         surface =
             new gfxXlibSurface(DefaultScreenOfDisplay(DefaultXDisplay()),
                                xdesc.XID(), incFormat, xdesc.size());
     }
 #endif
 
     mSentPaintNotification = PR_FALSE;
-    if (mFrontSurface) {
-#ifdef MOZ_X11
-        if (mFrontSurface->GetType() == gfxASurface::SurfaceTypeXlib) {
-            gfxXlibSurface *xsurf = static_cast<gfxXlibSurface*>(mFrontSurface.get());
-            *prevSurface =
-                SurfaceDescriptorX11(xsurf->XDrawable(), xsurf->XRenderFormat()->id,
-                                    mFrontSurface->GetSize());
-        } else
-#endif
-        if (gfxSharedImageSurface::IsSharedImage(mFrontSurface)) {
-            *prevSurface = static_cast<gfxSharedImageSurface*>(mFrontSurface.get())->GetShmem();
-        } else {
-            *prevSurface = null_t();
-        }
-    } else {
+
+    if (mFrontSurface && gfxSharedImageSurface::IsSharedImage(mFrontSurface))
+        *prevSurface = static_cast<gfxSharedImageSurface*>(mFrontSurface.get())->GetShmem();
+    else
         *prevSurface = null_t();
-    }
+
     mFrontSurface = surface;
     RecvNPN_InvalidateRect(updatedRect);
-#ifdef MOZ_X11
-    // Sync prevSurface before sending to child
-    if (prevSurface->type() == SurfaceDescriptor::TSurfaceDescriptorX11) {
-        XSync(DefaultXDisplay(), False);
-    }
-#endif
 
     return true;
 }
 
 nsresult
 PluginInstanceParent::AsyncSetWindow(NPWindow* aWindow)
 {
     NPRemoteWindow window;