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

...o the main branch
pinch is used, and I checked the logic for my scroll method is identical to smooth_scroll.  what I want to do is to take screenshots *while* UI action is happening, like, when I am in the middle of flipping images and two half-images are showing on the screen at the same time.  In order to do this, I have to complete the action without release(), take screenshot, and do release afterwards. Like:
        finger = self.scroll(self._current_image_locator,'left', 5, release=False)
        self.take_screenshot()
        finger.release()
        finger.perform()