Share menu missing or misplaced

[adamjernst]

@marcia in #88:

i'm trying it out right now on jason's ipad1 -- pressing the share button doesn't bring up anything for me to choose twitter/fb

edit: closing completely from task tray, it pops up for me now, though when i rotate to portrait mode the pointy thingie is on top of "download" and not "share"

edit2: and if i start out in portrait, tap share, and then rotate to landscape, the pointy is centered above the subtitles

[adamjernst]

There are two bugs.

1. The share menu sometimes stops appearing. Not sure how to repro.
2. Rotating leaves the share menu misplaced. This is a straightforward repro but harder fix due to the communication needed between HTML and native (about the share button's position).