sizing attribute broken when using custom property apis

[dman777]

Description

The attribute sizing will be broken if --iron-image-width and --iron-image-height are used instead of width and height html attributes.

Note: this is with using placeholder="data:image/jpeg;base64,... base64 image

Expected outcome

Image will show with sizing="cover", --iron-image-width, and --iron-image-height

Actual outcome

Image does not show at all and image element takes no space on doc flow.

Live Demo

Steps to reproduce

Browsers Affected

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

[Splaktar]

With "version": "1.2.3" I'm not able to get data URLs to work at all on Chrome 56. It seems like when it adds it via a background-image style using a url(data:image/jpeg;base64,...) it is leaving off the data:image/ part of the URL. It looked something like url(jpeg;base64,...).