call = function(){
    		clearInterval(id);
	        id = null;
	        fn.apply(scope, args || []);
	    }
@class Ext.util.DelayedTask
<p> The DelayedTask class provides a convenient way to "buffer" the execution of a method,
performing setTimeout where a new timeout cancels the old timeout. When called, the
task will wait the specified time period before executing. If durng that time period,
the task is called again, the original call will be cancelled. This continues so that
the function is only called a single time for each iteration.</p>
<p>This method is especially useful for things like detecting whether a user has finished
typing in a text field. An example would be performing validation on a keypress. You can
use this class to buffer the keypress events for a certain number of milliseconds, and
perform only if they stop for that amount of time.  Usage:</p><pre><code>
var task = new Ext.util.DelayedTask(function(){
    alert(Ext.getDom('myInputField').value.length);
});
// Wait 500ms before calling our function. If the user presses another key 
// during that 500ms, it will be cancelled and we'll wait another 500ms.
Ext.get('myInputField').on('keypress', function(){
    task.{@link #delay}(500); 
});
</code></pre> 
<p>Note that we are using a DelayedTask here to illustrate a point. The configuration
option <tt>buffer</tt> for {@link Ext.util.Observable#addListener addListener/on} will
also setup a delayed task for you to buffer events.</p> 
@constructor The parameters to this constructor serve as defaults and are not required.
@param {Function} fn (optional) The default function to call.
@param {Object} scope The default scope (The <code><b>this</b></code> reference) in which the
function is called. If not specified, <code>this</code> will refer to the browser window.
@param {Array} args (optional) The default Array of arguments.