HWUI: do not call glCopyTexSubImage2D on empty area.

Previous check .isEmpty() is not sufficient, because getWidth() may have
value 0.5, so technically it is not empty, but when this size is passed
to texture calls it is converted to uint_32 and it becomes zero.

bug:28941093
Change-Id: Ia7c2bf0340466d5376f235fb5da54ad2ddfa0a03
1 file changed