Issue Summary

Larger 2-3MB and complex HTML files slow down the interaction of the attachment while previewing. The file needs to load fully before X or scroll are ready to interact. 

Steps to Reproduce

1. Open a Jira work item which contains an HTML attachment with various complex formatting like tables, css, etc.
2. Open the file in preview.
3. The file needs to load first before X or scroll becomes available for interaction.
4. Sometimes the entire browser might freeze.

Expected Results

Interacting with X button should be avialable even before the attachment gets parsed and rendered in the browser. 

Actual Results

Depending on the end user's browser capabilities, the file might take a while to load or sometimes even freeze/crash the browser.

Workaround

Download the file and preview it in html reader of choice.