Read activity: does not show bookmarks when resuming

[erikos]

Steps to reproduce:

- open a pdf with Read

- create a bookmark on the first page

- close Read

- resume Read

---> the bookmark is not shown

- scroll a bit around to trigger a reload

---> bookmark is shown

As well you can create a new bookmark on the first page after resuming (as far as I understood the logic clicking on the bookmark icon when there is already one deletes it).

[humitos]

I could reproduce this in XO 1.75 os 12. The issue happens only with the first page. I tested this in another pages and the bookmark is shown properly.

[humitos]

 http://git.sugarlabs.org/read/mainline/commit/4b3a74a84a5bcfd95a1b3d49c682c036fb095660

This will be available in v100