Bug 1054326: Initial attempt to submit Imagecompare test framework and test cases int...

...o the main branch
You should be able to do this by switching to the system app and locating the status bar. Something like:
```python
from gaiatest.apps.system.app import System
m.switch_to_frame()
status_bar = m.find_element(*System._status_bar_locator)
print 'STATUS BAR\n=========='
print 'Displayed: %s' % status_bar.is_displayed()
print 'Location: %s' % status_bar.location
print 'Size: %s' % status_bar.size
```
This should tell you if the status bar is displayed, where it's located (always top left), and the size. You should be able to use this information to conditionally crop it from the screenshots.
```
 STATUS BAR
==========
Displayed: True
Location: {u'y': 0, u'x': 0}
Size: {u'width': 320, u'height': 30}
```