Usage of nsIPluginInstance Interface

 Returns the plugin instance if it has already been instantiated. This
 will never instantiate the plugin and so is safe to call even when
 content script must not execute.

[noscript] readonly attribute nsIPluginInstance pluginInstance

 Makes sure that a frame for this object exists, and that the plugin is
 instantiated. This method does nothing if the type is not #TYPE_PLUGIN.
 There is no guarantee that there will be a frame after this method is
 called; for example, the node may have a display:none style. If plugin
 instantiation is possible, it will be done synchronously by this method,
 and the plugin instance will be returned. A success return value does not
 necessarily mean that the instance is nonnull.

 This is a noscript method because it is internal and will go away once
 plugin loading moves to content.

 @note If there is an error instantiating the plugin, this method will
 trigger fallback to replacement content, and the type will change (and
 this method will return a failure code)

[noscript] nsIPluginInstance ensureInstantiation()

 Get the plugin name for the plugin instance.
 @param aInstance the plugin instance object
 @param aPluginName returns a pointer to a shared readonly string value,
        it's only valid for the lifetime of the plugin instance - you must
        copy the string value if you need it longer than that.

[noscript] void getPluginName(in nsIPluginInstance aInstance, [shared] out string aPluginName)

 To notify the plugin manager that the plugin created a script object 

[noscript] void setIsScriptableInstance(in nsIPluginInstance aInstance, in boolean aScriptable)

 Let the owner know what its instance is

void setInstance(in nsIPluginInstance aInstance)