common: revise canvas interfaces.

common: revise canvas interfaces.

1. removed async option which doesn't work currently,
rather than it, we can add async option in initiailizer class.

2. removed update() method.
Instead, we can call update(paint = nullptr); which has exactly same behavior.

Change-Id: I7909a50d804b97baf413a2ff6365a3cf79a3689e