Bug 1005733 - [email/UI] Cards's click-eating logic calls stopPropagation() but not preventDefault()
Change originally from :asuth, but reapplied to latest master
Merge pull request #21369 from jrburke/bug1005733-email-click-default

Bug 1005733 - [email/UI] Cards's click-eating logic calls stopPropagation() but not preventDefault() r=asuth