--- a/ipc/glue/WindowsMessageLoop.cpp
+++ b/ipc/glue/WindowsMessageLoop.cpp
@@ -201,27 +201,30 @@ ProcessOrDeferMessage(HWND hwnd,
     // Messages that can be deferred as-is. These must not contain pointers in
     // their wParam or lParam arguments!
     case WM_ACTIVATE:
     case WM_ACTIVATEAPP:
     case WM_CANCELMODE:
     case WM_CAPTURECHANGED:
     case WM_CHILDACTIVATE:
     case WM_DESTROY:
+    case WM_DISPLAYCHANGE:
     case WM_ENABLE:
     case WM_IME_NOTIFY:
     case WM_IME_SETCONTEXT:
+    case WM_KEYDOWN:
+    case WM_KEYUP:
     case WM_KILLFOCUS:
     case WM_MOUSEWHEEL:
     case WM_NCDESTROY:
     case WM_PARENTNOTIFY:
     case WM_SETFOCUS:
     case WM_SYSCOMMAND:
-    case WM_DISPLAYCHANGE:
-    case WM_SHOWWINDOW: // Intentional fall-through.
+    case WM_SHOWWINDOW:
+    case WM_VSCROLL: // Intentional fall-through.
     case WM_XP_THEMECHANGED: {
       deferred = new DeferredSendMessage(hwnd, uMsg, wParam, lParam);
       break;
     }
 
     case WM_DEVICECHANGE:
     case WM_POWERBROADCAST:
     case WM_NCACTIVATE: // Intentional fall-through.
@@ -319,17 +322,21 @@ ProcessOrDeferMessage(HWND hwnd,
 
         wchar_t className[256] = { 0 };
         if (GetClassNameW(hwnd, className, sizeof(className) - 1) > 0) {
           log.AppendLiteral(" (\"");
           log.Append(NS_ConvertUTF16toUTF8((PRUnichar*)className));
           log.AppendLiteral("\")");
         }
 
-        log.AppendLiteral(", sending it to DefWindowProc instead of the normal "
+        log.AppendLiteral(", wParam = ");
+        log.AppendInt(wParam);
+        log.AppendLiteral(", lParam = ");
+        log.AppendInt(lParam);
+        log.AppendLiteral("; sending it to DefWindowProc instead of the normal "
                           "window procedure.");
         NS_ERROR(log.get());
 #endif
         return DefWindowProc(hwnd, uMsg, wParam, lParam);
       }
     }
   }
 

--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -576,47 +576,63 @@ nsWindow::Create(nsIWidget *aParent,
     return NS_ERROR_FAILURE;
   }
 
   if (mIsRTL && nsUXThemeData::dwmSetWindowAttributePtr) {
     DWORD dwAttribute = TRUE;    
     nsUXThemeData::dwmSetWindowAttributePtr(mWnd, DWMWA_NONCLIENT_RTL_LAYOUT, &dwAttribute, sizeof dwAttribute);
   }
 
-  if (mWindowType != eWindowType_plugin &&
-      mWindowType != eWindowType_invisible &&
+  if ((mWindowType == eWindowType_toplevel ||
+       mWindowType == eWindowType_dialog ||
+       mWindowType == eWindowType_popup) &&
       MouseScrollHandler::Device::IsFakeScrollableWindowNeeded()) {
-    // Ugly Thinkpad Driver Hack (Bugs 507222 and 594977)
+    // Ugly Thinkpad Driver Hack (Bugs 507222, 594977 and 725475)
     //
-    // We create two zero-sized windows as descendants of the top-level window,
-    // like so:
+    // We create three zero-sized windows as descendants of the top-level
+    // window, like so:
     //
     //   Top-level window (MozillaWindowClass)
     //     FAKETRACKPOINTSCROLLCONTAINER (MozillaWindowClass)
     //       FAKETRACKPOINTSCROLLABLE (MozillaWindowClass)
+    //     FAKETRACKPOINTSCROLLBAR (ScrollBar)
     //
-    // We need to have the middle window, otherwise the Trackpoint driver
+    // We need to have the container window, otherwise the Trackpoint driver
     // will fail to deliver scroll messages.  WM_MOUSEWHEEL messages are
     // sent to the FAKETRACKPOINTSCROLLABLE, which then propagate up the
     // window hierarchy until they are handled by nsWindow::WindowProc.
     // WM_HSCROLL messages are also sent to the FAKETRACKPOINTSCROLLABLE,
     // but these do not propagate automatically, so we have the window
     // procedure pretend that they were dispatched to the top-level window
     // instead.
     //
     // The FAKETRACKPOINTSCROLLABLE needs to have the specific window styles it
     // is given below so that it catches the Trackpoint driver's heuristics.
+    //
+    // The FAKETRACKPOINTSCROLLBAR is needed for certain configurations of
+    // Synaptics drivers when a plugin window is visible and would otherwise
+    // attract all scrolling messages.  A corresponding horizontal scrollbar
+    // does not seem to be needed to attract WM_HSCROLL messages.
     HWND scrollContainerWnd = ::CreateWindowW
       (className.get(), L"FAKETRACKPOINTSCROLLCONTAINER",
        WS_CHILD | WS_VISIBLE,
        0, 0, 0, 0, mWnd, NULL, nsToolkit::mDllInstance, NULL);
     HWND scrollableWnd = ::CreateWindowW
       (className.get(), L"FAKETRACKPOINTSCROLLABLE",
        WS_CHILD | WS_VISIBLE | WS_VSCROLL | WS_TABSTOP | 0x30,
        0, 0, 0, 0, scrollContainerWnd, NULL, nsToolkit::mDllInstance, NULL);
+    HWND scrollBarWnd = ::CreateWindowW
+      (L"SCROLLBAR", L"FAKETRACKPOINTSCROLLBAR",
+       WS_CHILD | WS_VISIBLE | SBS_VERT,
+       0, 0, 0, 0, mWnd, NULL, nsToolkit::mDllInstance, NULL);
+
+    // We set the hidden scroll bar control to have a range of values and
+    // be positioned in the middle, so that scrolling up and down works.
+    SCROLLINFO scrollInfo = { sizeof SCROLLINFO, SIF_ALL, 0, 100, 1, 50, 50 };
+    ::SetScrollInfo(scrollBarWnd, SB_CTL, &scrollInfo, FALSE);
 
     // Give the FAKETRACKPOINTSCROLLABLE window a specific ID so that
     // WindowProcInternal can distinguish it from the top-level window
     // easily.
     ::SetWindowLongPtrW(scrollableWnd, GWLP_ID, eFakeTrackPointScrollableID);
 
     // Make FAKETRACKPOINTSCROLLABLE use nsWindow::WindowProc, and store the
     // old window procedure in its "user data".
@@ -6848,21 +6864,19 @@ nsWindow::SetWindowClipRegion(const nsTA
   }
 
   // If a plugin is not visible, especially if it is in a background tab,
   // it should not be able to steal keyboard focus.  This code checks whether
   // the region that the plugin is being clipped to is NULLREGION.  If it is,
   // the plugin window gets disabled.
   if(mWindowType == eWindowType_plugin) {
     if(NULLREGION == ::CombineRgn(dest, dest, dest, RGN_OR)) {
-      ::ShowWindow(mWnd, SW_HIDE);
       ::EnableWindow(mWnd, FALSE);
     } else {
       ::EnableWindow(mWnd, TRUE);
-      ::ShowWindow(mWnd, SW_SHOW);
     }
   }
   if (!::SetWindowRgn(mWnd, dest, TRUE)) {
     ::DeleteObject(dest);
     return NS_ERROR_FAILURE;
   }
   return NS_OK;
 }