iron list ist destroying layout

[jogibear9988]

Description

If I scroll down in my iron list, all items are at one place

Issue

Iron List uses every time the first item to calculate the items size, see:

iron-list/iron-list.html

Line 1290 in 0c9a669

this._rowHeight = this._physicalCount > 0 ? this._physicalItems[0].offsetHeight : 200;

problem is, if the first item in this list is invisible, the offsetWidth and Height are "0"

Browsers Affected

• Chrome
• Firefox
• Safari 9
• Safari 8
• Safari 7
• Edge
• IE 11
• IE 10

[jogibear9988]

see offsetHeight is 0 (even if the computed style is not "0")