Bug 564260 - Fix for plugin hangs in [@ hang | KiFastSystemCallRet | NtUserSetFocus]. r=masayuki.

widget/src/windows/nsWindow.cpp

@@ -3845,6 +3845,8 @@ nsWindow::IPCWindowProcHandler(UINT& msg, WPARAM& wParam, LPARAM& lParam)
     // Windowed plugins that fire context menu selection events to parent
     // windows.
     case WM_CONTEXTMENU:
+    // IME events fired as a result of synchronous focus changes
+    case WM_IME_SETCONTEXT:
       handled = PR_TRUE;
     break;
   }