With the web clipper extension enabled, pages from the Boto3 website can take a very long time to load.
For example, this page takes close to 2 minutes on a corporate network: http://boto3.readthedocs.io/en/latest/reference/services/dynamodb.html
The offending request is:
Status Code:200 OK
I narrowed it down by first disabling all extensions and then enabling extensions one at a time until I found Web Clipper to be the problem.
All pages on this site are impacted, but the degree appears to correspond with the size of the page.
I really haven't a clue what the other site is doing...I imagine a lot of changes to the DOM that result in some rescan of the page by Web Clipper.