Custom HTTP header in the AppCache requests

Question

Is it possible to add a custom HTTP header to each request executed as a cache update?

i.e. cache.manifest

CACHE MANIFEST

CACHE:
/page1.html
/page2.html

I would like the requests for the page1.html and page2.html be executed with a custom HTTP header of X-Custom-Header: foo

Answer 1

Answering my own question:

It appears the custom headers from the original request will be applied to the app cache request as well.

So when I'm accessing page1.html I need to set the custom header. When the app cache requests the page2.html it will do so with the same custom header.