http://kb.mozillazine.org/Plugin-container_and_out-of-process_plugins
Disabling crash protection
go to about:config and set all dom.ipc.plugins.enabled.* preferences to false. This will prevent the "plugin-container" process from running and all plugins will run within the Firefox browser process.
On
Linux:
dom.ipc.plugins.enabled.libflashplayer.so (Adobe Flash)
dom.ipc.plugins.enabled.libnptest.so (NPAPI test plugin)
On Windows:
dom.ipc.plugins.enabled.npctrl.dll (Microsoft
Silverlight)
dom.ipc.plugins.enabled.npqtplugin.dll (Apple QuickTime)
dom.ipc.plugins.enabled.npswf32.dll (Adobe Flash)
dom.ipc.plugins.enabled.nptest.dll (NPAPI test plugin)
Toggle (double-click) each preference to change the value from
"true" to false.
--
firefox 4 beta13pre 中，只需要设定一项内容足够了，如下user.js片段所示。
//关闭plugin-container进程
user_pref("dom.ipc.plugins.enabled", false);