Issue title: Website buttons on certain pages dont fully display embedded image
 Issue body: This should have the facebook logo displayed in it.

![screen shot 2018-10-10 at 11 13 05 pm](https://user-images.githubusercontent.com/39230578/46780455-6570e800-cd0c-11e8-9eb9-3ab537a853c2.png)

 Comments: 
 Comment 0: This appears to work for me in my latest build.. and for you? (testing heavily my latest ContentPolicy changes... so testing random websites and noticed)
 Comment 1: Still flaky on a few sites for me. Probably slight differences in our installed packages for our build environments.
 Comment 2: Do you have references to these flaky site so we can try who .18 performs?
{'source': 'GithubIssues', 'repo_name_with_owner': 'wicknix/Arctic-Fox', 'issue_id': 368946486, 'repo_stars': 188.0}