Fixes mootools#2247.

This fixes a nasty regression that custom attributes set by HTML text
(e.g. innerHTML) would previously be considered `expando` and therefore
thought to have been considered a fake attribute. Therefore, we didn't
return the value.

This fix relies now on outerHTML to check for the existence of the
attribute. Keep in mind this also fixes the previous bug of returning
custom functions since any new `el.attribute =` are not shown in
outerHTML.

PASSED: IE6-9.

Source/Element/Element.js

@@ -607,6 +607,9 @@ Element.implement({
 		} else {
 			if (value == null){
 				this.removeAttribute(name);
+				/* <ltIE9> */
+				if (pollutesGetAttribute) delete attributeWhiteList[name];
+				/* </ltIE9> */
 			} else {
 				this.setAttribute(name, value);
 				/* <ltIE9> */
@@ -627,8 +630,9 @@ Element.implement({
 		if (getter) return getter(this);
 		/* <ltIE9> */
 		if (pollutesGetAttribute && !attributeWhiteList[name]){
-			var attr = this.getAttributeNode(name);
-			if (!attr || attr.expando) return null;
+			var outer = this.outerHTML, i = outer.indexOf(name);
+			if ((i < 0) || (i > outer.indexOf('><'))) return null;
+			attributeWhiteList[name] = true;
 		}
 		/* </ltIE9> */
 		var result = Slick.getAttribute(this, name);

Specs/1.4client/Element/Element.js

@@ -26,6 +26,20 @@ describe('Element', function(){
 			expect(div.getProperty('random')).toEqual('attribute');
 		});
 
+		it('should get custom attributes in html', function(){
+			var div = new Element('div', {html: '<div data-load="test"></div>'}).getFirst();
+			expect(div.get('data-load')).toEqual('test');
+
+			div = new Element('div', {html: '<div data-custom></div>'}).getFirst();
+			expect(div.get('data-custom')).toEqual('');
+
+			div = new Element('div', {html: '<div data-custom="test"><a data-custom="other"></a></div>'}).getFirst();
+			expect(div.get('data-custom')).toEqual('test');
+
+			div = new Element('div', {html: '<div><a data-custom="other"></a></div>'}).getFirst();
+			expect(div.get('data-custom')).toEqual(null);
+		});
+
 	});
 
 	describe('Element.set', function(){