Scale the origin for the Draw Layer (Calc Tiled Rendering).

Since we're changing units, we also need to scale the origin
by the correct amount.

Change-Id: Ie0563376e8fa56f20c30da4fe3cc50546f18e84f
Use logic units for visible-cells determination.

This eliminates a bunch of LogicToPixel conversions, and also
means that tiles starting other than the origin are correctly
processed (as LogicToPixel run on a rectangle will also move that
rectangle depending on the origin set in the output device).

Change-Id: I42903fe23ad5f6baa1d5276d5dcc7ee038bd27cf
Iterate from origin to tile area to ensure correct positioning.

Change-Id: I29e881f9e67b84e208a198d2aad06db382d14698